diff --git a/app/services/repositories/compare_service.rb b/app/services/repositories/compare_service.rb
new file mode 100644
index 00000000..c2e5df45
--- /dev/null
+++ b/app/services/repositories/compare_service.rb
@@ -0,0 +1,35 @@
+class Repositories::CompareService < ApplicationService
+  attr_reader :owner, :project, :params
+
+  def initialize(owner, project, params)
+    @owner = owner
+    @project = project
+    @params  = params
+  end
+
+  def call
+    compare!
+  rescue => e
+    raise Error, e.message
+  end
+
+  private
+
+  def compare!
+    base, head = compare_params
+
+    # TODO: 处理fork的项目向源项目发送PR的base、head参数问题
+    head.include?(":") ? gitea_compare(base, head) : gitea_compare(head, base)
+  end
+
+  def compare_params
+    base = Addressable::URI.unescape(params[:base])
+    head = params[:head].include?('json') ? params[:head]&.split('.json')[0] : params[:head]
+
+    [base, head]
+  end
+
+  def gitea_compare(base, head)
+    Gitea::Repository::Commits::CompareService.call(@owner.login, @project.identifier, base, head)
+  end
+end