diff --git a/source/libs/scalar/src/sclfunc.c b/source/libs/scalar/src/sclfunc.c
index 4d57af822e..a3806893c7 100644
--- a/source/libs/scalar/src/sclfunc.c
+++ b/source/libs/scalar/src/sclfunc.c
@@ -331,6 +331,19 @@ static int32_t concatCopyHelper(const char *input, char *output, bool hasNcharCo
   return TSDB_CODE_SUCCESS;
 }
 
+static int32_t getNumOfNullEntries(SColumnInfoData *pColumnInfoData, int32_t numOfRows) {
+  int32_t numOfNulls = 0;
+  if (!pColumnInfoData->hasNull) {
+    return numOfNulls;
+  }
+  for (int i = 0; i < numOfRows; ++i) {
+    if (pColumnInfoData->varmeta.offset[i] == -1) {
+      numOfNulls++;
+    }
+  }
+  return numOfNulls;
+}
+
 int32_t concatFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput) {
   if (inputNum < 2 || inputNum > 8) { // concat accpet 2-8 input strings
     return TSDB_CODE_FAILED;
@@ -363,10 +376,12 @@ int32_t concatFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOu
     if (hasNcharCol && (GET_PARAM_TYPE(&pInput[i]) == TSDB_DATA_TYPE_VARCHAR)) {
       factor = TSDB_NCHAR_SIZE;
     }
+
+    int32_t numOfNulls = getNumOfNullEntries(pInputData[i], pInput[i].numOfRows);
     if (pInput[i].numOfRows == 1) {
-      inputLen += (pInputData[i]->varmeta.length - VARSTR_HEADER_SIZE) * factor * numOfRows;
+      inputLen += (pInputData[i]->varmeta.length - VARSTR_HEADER_SIZE) * factor * (numOfRows - numOfNulls);
     } else {
-      inputLen += pInputData[i]->varmeta.length - numOfRows * VARSTR_HEADER_SIZE;
+      inputLen += pInputData[i]->varmeta.length - (numOfRows - numOfNulls) * VARSTR_HEADER_SIZE;
     }
   }
 
@@ -444,13 +459,15 @@ int32_t concatWsFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *p
     if (hasNcharCol && (GET_PARAM_TYPE(&pInput[i]) == TSDB_DATA_TYPE_VARCHAR)) {
       factor = TSDB_NCHAR_SIZE;
     }
+
+    int32_t numOfNulls = getNumOfNullEntries(pInputData[i], pInput[i].numOfRows);
     if (i == 0) {
       // calculate required separator space
-      inputLen += (pInputData[0]->varmeta.length - VARSTR_HEADER_SIZE) * numOfRows * (inputNum - 2) * factor;
+      inputLen += (pInputData[0]->varmeta.length - VARSTR_HEADER_SIZE) * (numOfRows - numOfNulls) * (inputNum - 2) * factor;
     } else if (pInput[i].numOfRows == 1) {
-      inputLen += (pInputData[i]->varmeta.length - VARSTR_HEADER_SIZE) * numOfRows * factor;
+      inputLen += (pInputData[i]->varmeta.length - VARSTR_HEADER_SIZE) * (numOfRows - numOfNulls) * factor;
     } else {
-      inputLen += pInputData[i]->varmeta.length - numOfRows * VARSTR_HEADER_SIZE;
+      inputLen += pInputData[i]->varmeta.length - (numOfRows - numOfNulls) * VARSTR_HEADER_SIZE;
     }
   }
 
diff --git a/tests/script/tsim/query/charScalarFunction.sim b/tests/script/tsim/query/charScalarFunction.sim
index afdb9e0d74..1be4a4a4bf 100644
--- a/tests/script/tsim/query/charScalarFunction.sim
+++ b/tests/script/tsim/query/charScalarFunction.sim
@@ -266,20 +266,21 @@ if $data11 != NULL then
   return -1
 endi
 
-# print ====> select c2, c3 , concat(c2,c3) from ctb6
-# sql select c2, c3 , concat(c2,c3) from ctb6
-# print ====> rows: $rows
-# print ====> $data00 $data01 $data02
-# print ====> $data10 $data11 $data12
-# if $rows != 2 then
-#   return -1
-# endi
-# if $data02 != 中文测试01中文测试01 then
-#   return -1
-# endi
-# if $data12 != NULL then
-#   return -1
-# endi
+print ====> select c2, c3 , concat(c2,c3) from ctb6
+sql select c2, c3 , concat(c2,c3) from ctb6
+print ====> rows: $rows
+print ====> $data00 $data01 $data02
+print ====> $data10 $data11 $data12
+if $rows != 2 then
+  return -1
+endi
+if $data02 != 中文测试1中文测试2 then
+  return -1
+endi
+if $data12 != NULL then
+  return -1
+endi
+return
 
 print ====> select c2, c3 , concat(c2,c3) from ntb6
 sql select c2, c3 , concat(c2,c3) from ntb6