diff --git a/CMakeLists.txt b/CMakeLists.txt
index dae8956..b86c9bf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -20,6 +20,7 @@ set(NASAL_OBJECT_SOURCE_FILE
     ${CMAKE_SOURCE_DIR}/src/ast_visitor.cpp
     ${CMAKE_SOURCE_DIR}/src/nasal_ast.cpp
     ${CMAKE_SOURCE_DIR}/src/nasal_builtin.cpp
+    ${CMAKE_SOURCE_DIR}/src/coroutine.cpp
     ${CMAKE_SOURCE_DIR}/src/fg_props.cpp
     ${CMAKE_SOURCE_DIR}/src/math_lib.cpp
     ${CMAKE_SOURCE_DIR}/src/nasal_codegen.cpp
diff --git a/makefile b/makefile
index 636cd5f..713cd42 100644
--- a/makefile
+++ b/makefile
@@ -18,7 +18,8 @@ NASAL_HEADER=\
 	src/optimizer.h\
 	src/symbol_finder.h\
 	src/fg_props.h\
-	src/math_lib.h
+	src/math_lib.h\
+	src/coroutine.h
 
 NASAL_OBJECT=\
 	build/nasal_err.o\
@@ -37,6 +38,7 @@ NASAL_OBJECT=\
 	build/nasal_builtin.o\
 	build/fg_props.o\
 	build/math_lib.o\
+	build/coroutine.o\
 	build/nasal_vm.o\
 	build/nasal_dbg.o\
 	build/main.o
@@ -89,6 +91,12 @@ build/nasal_builtin.o: \
 	src/nasal_builtin.h src/nasal_builtin.cpp | build
 	$(CXX) -std=$(STD) -c -O3 src/nasal_builtin.cpp -fno-exceptions -fPIC -o build/nasal_builtin.o -I .
 
+build/coroutine.o: \
+	src/nasal.h\
+	src/nasal_gc.h\
+	src/coroutine.h src/coroutine.cpp | build
+	$(CXX) -std=$(STD) -c -O3 src/coroutine.cpp -fno-exceptions -fPIC -o build/coroutine.o -I .
+
 build/math_lib.o: \
 	src/nasal.h\
 	src/nasal_gc.h\
diff --git a/src/coroutine.cpp b/src/coroutine.cpp
new file mode 100644
index 0000000..ea10295
--- /dev/null
+++ b/src/coroutine.cpp
@@ -0,0 +1,116 @@
+#include "coroutine.h"
+
+var builtin_cocreate(var* local, gc& ngc) {
+    // +-------------+
+    // | old pc      | <- top[0]
+    // +-------------+
+    // | old localr  | <- top[-1]
+    // +-------------+
+    // | old upvalr  | <- top[-2]
+    // +-------------+
+    // | local scope |
+    // | ...         |
+    // +-------------+ <- local pointer stored in localr
+    // | old funcr   | <- old function stored in funcr
+    // +-------------+
+    var func = local[1];
+    if (func.type!=vm_func) {
+        return nas_err("coroutine::create", "must use a function to create coroutine");
+    }
+    if (ngc.cort) {
+        return nas_err("coroutine::create", "cannot create another coroutine in a coroutine");
+    }
+    var co = ngc.alloc(vm_co);
+    nas_co& cort = co.co();
+    cort.ctx.pc = func.func().entry-1;
+
+    cort.ctx.top[0] = nil;
+    cort.ctx.localr = cort.ctx.top+1;
+    cort.ctx.top = cort.ctx.localr+func.func().lsize;
+    cort.ctx.localr[0] = func.func().local[0];
+    cort.ctx.top[0] = nil; // old upvalr
+    cort.ctx.top++;
+    cort.ctx.top[0] = var::addr((var*)nullptr); // old localr
+    cort.ctx.top++;
+    cort.ctx.top[0] = var::ret(0); // old pc, set to zero to make op_ret recognizing this as coroutine function
+
+    cort.ctx.funcr = func; // make sure the coroutine function can use correct upvalues
+    cort.status = nas_co::status::suspended;
+    
+    return co;
+}
+
+var builtin_coresume(var* local, gc& ngc) {
+    if (ngc.cort) {
+        return nas_err("coroutine::resume", "cannot start another coroutine when one is running");
+    }
+    var co = local[1];
+    // return nil if is not a coroutine object
+    if (co.type!=vm_co) {
+        return nil;
+    }
+    // cannot resume a dead coroutine
+    if (co.co().status==nas_co::status::dead) {
+        return nil;
+    }
+
+    // change to coroutine context
+    ngc.ctxchg(co.co());
+
+    // fetch coroutine's stack top and return
+    // so the coroutine's stack top in fact is not changed
+    if (ngc.rctx->top[0].type==vm_ret) {
+        // when first calling this coroutine, the stack top must be vm_ret
+        return ngc.rctx->top[0];
+    }
+
+    // after first calling the coroutine, each time coroutine.yield triggered
+    // a new space will be reserved on stack with value nil
+    // so we could fill this place with args
+
+    // the coroutine seems like coroutine.yield returns the value
+    // but in fact coroutine.yield stop the coroutine
+    // until main context calls the coroutine.resume
+    return local[2];
+}
+
+var builtin_coyield(var* local, gc& ngc) {
+    if (!ngc.cort) {
+        return nas_err("coroutine::yield", "no coroutine is running");
+    }
+
+    // this will set to main stack top
+    ngc.ctxreserve();
+    
+    // then this will return value to main's stack top[0]
+    // the procedure seems like coroutine.resume returns the value
+    // but in fact coroutine.resume stop the main context
+    // until coroutine calls the coroutine.yield
+    return local[1];
+}
+
+var builtin_costatus(var* local, gc& ngc) {
+    var co = local[1];
+    if (co.type!=vm_co) {
+        return ngc.newstr("error");
+    }
+    switch(co.co().status) {
+        case nas_co::status::suspended: return ngc.newstr("suspended");
+        case nas_co::status::running:   return ngc.newstr("running");
+        case nas_co::status::dead:      return ngc.newstr("dead");
+    }
+    return nil;
+}
+
+var builtin_corun(var* local, gc& ngc) {
+    return ngc.cort? one:zero;
+}
+
+nasal_builtin_table coroutine_native[] = {
+    {"__cocreate", builtin_cocreate},
+    {"__coresume", builtin_coresume},
+    {"__coyield", builtin_coyield},
+    {"__costatus", builtin_costatus},
+    {"__corun", builtin_corun},
+    {nullptr, nullptr}
+};
\ No newline at end of file
diff --git a/src/coroutine.h b/src/coroutine.h
new file mode 100644
index 0000000..83911aa
--- /dev/null
+++ b/src/coroutine.h
@@ -0,0 +1,13 @@
+#pragma once
+
+#include "nasal.h"
+#include "nasal_gc.h"
+#include "nasal_builtin.h"
+
+var builtin_cocreate(var*, gc&);
+var builtin_coresume(var*, gc&);
+var builtin_coyield(var*, gc&);
+var builtin_costatus(var*, gc&);
+var builtin_corun(var*, gc&);
+
+extern nasal_builtin_table coroutine_native[];
\ No newline at end of file
diff --git a/src/nasal_builtin.cpp b/src/nasal_builtin.cpp
index bf9b4a5..c42f94d 100644
--- a/src/nasal_builtin.cpp
+++ b/src/nasal_builtin.cpp
@@ -1040,112 +1040,6 @@ var builtin_md5(var* local, gc& ngc) {
     return ngc.newstr(md5(str.str()));
 }
 
-var builtin_cocreate(var* local, gc& ngc) {
-    // +-------------+
-    // | old pc      | <- top[0]
-    // +-------------+
-    // | old localr  | <- top[-1]
-    // +-------------+
-    // | old upvalr  | <- top[-2]
-    // +-------------+
-    // | local scope |
-    // | ...         |
-    // +-------------+ <- local pointer stored in localr
-    // | old funcr   | <- old function stored in funcr
-    // +-------------+
-    var func = local[1];
-    if (func.type!=vm_func) {
-        return nas_err("coroutine::create", "must use a function to create coroutine");
-    }
-    if (ngc.cort) {
-        return nas_err("coroutine::create", "cannot create another coroutine in a coroutine");
-    }
-    var co = ngc.alloc(vm_co);
-    nas_co& cort = co.co();
-    cort.ctx.pc = func.func().entry-1;
-
-    cort.ctx.top[0] = nil;
-    cort.ctx.localr = cort.ctx.top+1;
-    cort.ctx.top = cort.ctx.localr+func.func().lsize;
-    cort.ctx.localr[0] = func.func().local[0];
-    cort.ctx.top[0] = nil; // old upvalr
-    cort.ctx.top++;
-    cort.ctx.top[0] = var::addr((var*)nullptr); // old localr
-    cort.ctx.top++;
-    cort.ctx.top[0] = var::ret(0); // old pc, set to zero to make op_ret recognizing this as coroutine function
-
-    cort.ctx.funcr = func; // make sure the coroutine function can use correct upvalues
-    cort.status = nas_co::status::suspended;
-    
-    return co;
-}
-
-var builtin_coresume(var* local, gc& ngc) {
-    if (ngc.cort) {
-        return nas_err("coroutine::resume", "cannot start another coroutine when one is running");
-    }
-    var co = local[1];
-    // return nil if is not a coroutine object
-    if (co.type!=vm_co) {
-        return nil;
-    }
-    // cannot resume a dead coroutine
-    if (co.co().status==nas_co::status::dead) {
-        return nil;
-    }
-
-    // change to coroutine context
-    ngc.ctxchg(co.co());
-
-    // fetch coroutine's stack top and return
-    // so the coroutine's stack top in fact is not changed
-    if (ngc.rctx->top[0].type==vm_ret) {
-        // when first calling this coroutine, the stack top must be vm_ret
-        return ngc.rctx->top[0];
-    }
-
-    // after first calling the coroutine, each time coroutine.yield triggered
-    // a new space will be reserved on stack with value nil
-    // so we could fill this place with args
-
-    // the coroutine seems like coroutine.yield returns the value
-    // but in fact coroutine.yield stop the coroutine
-    // until main context calls the coroutine.resume
-    return local[2];
-}
-
-var builtin_coyield(var* local, gc& ngc) {
-    if (!ngc.cort) {
-        return nas_err("coroutine::yield", "no coroutine is running");
-    }
-
-    // this will set to main stack top
-    ngc.ctxreserve();
-    
-    // then this will return value to main's stack top[0]
-    // the procedure seems like coroutine.resume returns the value
-    // but in fact coroutine.resume stop the main context
-    // until coroutine calls the coroutine.yield
-    return local[1];
-}
-
-var builtin_costatus(var* local, gc& ngc) {
-    var co = local[1];
-    if (co.type!=vm_co) {
-        return ngc.newstr("error");
-    }
-    switch(co.co().status) {
-        case nas_co::status::suspended: return ngc.newstr("suspended");
-        case nas_co::status::running:   return ngc.newstr("running");
-        case nas_co::status::dead:      return ngc.newstr("dead");
-    }
-    return nil;
-}
-
-var builtin_corun(var* local, gc& ngc) {
-    return ngc.cort? one:zero;
-}
-
 var builtin_millisec(var* local, gc& ngc) {
     f64 res = std::chrono::duration_cast<std::chrono::milliseconds>
             (std::chrono::high_resolution_clock::now().time_since_epoch())
@@ -1295,11 +1189,6 @@ nasal_builtin_table builtin[] = {
     {"__platform", builtin_platform},
     {"__arch", builtin_arch},
     {"__md5", builtin_md5},
-    {"__cocreate", builtin_cocreate},
-    {"__coresume", builtin_coresume},
-    {"__coyield", builtin_coyield},
-    {"__costatus", builtin_costatus},
-    {"__corun", builtin_corun},
     {"__millisec", builtin_millisec},
     {"__gcextd", builtin_gcextend},
     {"__gcinfo", builtin_gcinfo},
diff --git a/src/nasal_builtin.h b/src/nasal_builtin.h
index 85a8050..5c62658 100644
--- a/src/nasal_builtin.h
+++ b/src/nasal_builtin.h
@@ -109,11 +109,6 @@ var builtin_arch(var*, gc&);
 std::string tohex(u32);
 std::string md5(const std::string&);
 var builtin_md5(var*, gc&);
-var builtin_cocreate(var*, gc&);
-var builtin_coresume(var*, gc&);
-var builtin_coyield(var*, gc&);
-var builtin_costatus(var*, gc&);
-var builtin_corun(var*, gc&);
 var builtin_millisec(var*, gc&);
 var builtin_gcextend(var*, gc&);
 var builtin_gcinfo(var*, gc&);
diff --git a/src/nasal_codegen.cpp b/src/nasal_codegen.cpp
index 6d16310..3101188 100644
--- a/src/nasal_codegen.cpp
+++ b/src/nasal_codegen.cpp
@@ -15,6 +15,7 @@ void codegen::load_native_function_table(nasal_builtin_table* table) {
 void codegen::init_native_function() {
     load_native_function_table(builtin);
     load_native_function_table(math_lib_native);
+    load_native_function_table(coroutine_native);
     load_native_function_table(flight_gear_native);
 }
 
diff --git a/src/nasal_codegen.h b/src/nasal_codegen.h
index fbfe11b..3913790 100644
--- a/src/nasal_codegen.h
+++ b/src/nasal_codegen.h
@@ -9,6 +9,7 @@
 #include "nasal_import.h"
 
 #include "nasal_builtin.h"
+#include "coroutine.h"
 #include "math_lib.h"
 #include "fg_props.h"