diff --git a/cmake.sh b/cmake.sh
new file mode 100755
index 0000000..c81cef4
--- /dev/null
+++ b/cmake.sh
@@ -0,0 +1,2 @@
+cmake -S . -B build
+cmake --build build -j12
\ No newline at end of file
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 692c160..17fe54f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -19,6 +19,7 @@ add_executable(sysyc
   backend/llir.cc
   backend/assembly.cc
   opt/peephole.cc
+  opt/constprop.cc
 )
 target_include_directories(sysyc PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
 target_link_libraries(sysyc PRIVATE SysYParser)
diff --git a/src/opt/constprop.cc b/src/opt/constprop.cc
index 3cd01da..eac8ec8 100644
--- a/src/opt/constprop.cc
+++ b/src/opt/constprop.cc
@@ -1,3 +1,134 @@
+#include "constprop.h"
+#include "../frontend/IR.h"
+#include <unordered_map>
+#include <string>
+
 namespace transform {
-  
-}
\ No newline at end of file
+
+void ConstProp::functionTransform(sysy::Function *func) {
+    for (auto &bb : func->getBasicBlocks()) {
+        this->curBB = bb.get();
+        this->constantPropagation(bb.get());
+    }
+}
+
+void ConstProp::moduleTransform() {
+    auto *funcs = this->module->getFunctions();
+    for (auto it = funcs->begin(); it != funcs->end(); ++it) {
+        this->functionTransform(it->second);
+    }
+}
+
+void ConstProp::constantPropagation(sysy::BasicBlock *bb) {
+    int flag;
+    std::unordered_map<std::string, std::string> valueMap;
+    std::unordered_map<std::string, std::string> valuechange;
+    for (auto &inst : bb->CoInst) {
+        if (inst.op == "li") { // Assuming 'li' is the instruction to load immediate constants.
+            valueMap[inst.fields[0]] = inst.fields[1]; // Store constant value with its register.
+            valuechange[inst.fields[0]] = "0";
+        }
+        else if(inst.op == "add" ){
+            for (int i=1;i<=2;i++){
+                flag = false;
+                if (inst.valid && !inst.fields.empty() && valueMap.find(inst.fields[i]) != valueMap.end() && valuechange[inst.fields[i]] == "0") {
+                    inst.fields[i] = valueMap[inst.fields[i]];
+                    flag = true;
+                }
+                else break;
+            }
+            if (flag){
+                int temp1 =  std::stoll(inst.fields[1]);
+                int temp2 =  std::stoll(inst.fields[2]);
+                valueMap[inst.fields[0]] = std::to_string(temp1 + temp2);
+            }
+            else{
+                valuechange[inst.fields[0]] = "1";
+            }
+        }
+        else if(inst.op == "sub" ){
+            for (int i=1;i<=2;i++){
+                flag = false;
+                if (inst.valid && !inst.fields.empty() && valueMap.find(inst.fields[i]) != valueMap.end() && valuechange[inst.fields[i]] == "0") {
+                    inst.fields[i] = valueMap[inst.fields[i]];
+                    flag = true;
+                }
+                else break;
+            }
+            if (flag){
+                int temp1 =  std::stoll(inst.fields[1]);
+                int temp2 =  std::stoll(inst.fields[2]);
+                valueMap[inst.fields[0]] = std::to_string(temp1 - temp2);
+            }
+            else{
+                valuechange[inst.fields[0]] = "1";
+            }
+        }
+        else if(inst.op == "mul" ){
+            for (int i=1;i<=2;i++){
+                flag = false;
+                if (inst.valid && !inst.fields.empty() && valueMap.find(inst.fields[i]) != valueMap.end() && valuechange[inst.fields[i]] == "0") {
+                    inst.fields[i] = valueMap[inst.fields[i]];
+                    flag = true;
+                }
+                else break;
+            }
+            if (flag){
+                int temp1 =  std::stoll(inst.fields[1]);
+                int temp2 =  std::stoll(inst.fields[2]);
+                valueMap[inst.fields[0]] = std::to_string(temp1 * temp2);
+            }
+            else{
+                valuechange[inst.fields[0]] = "1";
+            }
+        }
+        else if(inst.op == "div" ){
+            for (int i=1;i<=2;i++){
+                flag = false;
+                if (inst.valid && !inst.fields.empty() && valueMap.find(inst.fields[i]) != valueMap.end() && valuechange[inst.fields[i]] == "0") {
+                    inst.fields[i] = valueMap[inst.fields[i]];
+                    flag = true;
+                }
+                else break;
+            }
+            if (flag){
+                int temp1 =  std::stoll(inst.fields[1]);
+                int temp2 =  std::stoll(inst.fields[2]);
+                valueMap[inst.fields[0]] = std::to_string(temp1 / temp2);
+            }
+            else{
+                valuechange[inst.fields[0]] = "1";
+            }
+        }
+        else if (inst.op == "sw" ){ 
+            std::string temp;
+            auto nextInst = std::next(&inst);
+            if (inst.valid && !inst.fields.empty() && valueMap.find(inst.fields[0]) != valueMap.end() && valuechange[inst.fields[0]] == "0") {
+                // Replace uses of constants.
+                    //inst.fields[0] = valueMap[inst.fields[0]];
+                    temp = valueMap[inst.fields[0]];
+            }
+            if (nextInst->op == "lw"){
+                valueMap[nextInst->fields[0]] = temp;// Store constant value with its register.
+                valuechange[nextInst->fields[0]] = "0";
+            }
+        }
+        else if (inst.op == "lw" ){ 
+            continue;
+        }
+        // else if (inst.op == "addi" && inst.op == "ori" && inst.op == "subi"  && inst.op == "slli" && inst.op == "sll" ){
+        //     if (inst.valid && !inst.fields.empty() && valueMap.find(inst.fields[0]) != valueMap.end() && valuechange[inst.fields[0]] == "0") {
+        //         // Replace uses of constants.
+        //             valuechange[inst.fields[0]] = "1";
+        //     }
+        // }
+        else{
+           if (inst.valid && !inst.fields.empty() && valueMap.find(inst.fields[0]) != valueMap.end() && valuechange[inst.fields[0]] == "0") {
+                // Replace uses of constants.
+                    valuechange[inst.fields[0]] = "1";
+            }
+        }  
+    }
+
+}
+} // namespace transform
\ No newline at end of file
diff --git a/src/opt/constprop.h b/src/opt/constprop.h
index e69de29..e2c7fd0 100644
--- a/src/opt/constprop.h
+++ b/src/opt/constprop.h
@@ -0,0 +1,21 @@
+#include "../frontend/IR.h"
+
+namespace transform {
+
+class ConstProp {
+private:
+    sysy::Module *module;
+
+public:
+    sysy::BasicBlock *curBB;
+
+    ConstProp(sysy::Module *module): module(module) {};
+
+    void moduleTransform();
+    void functionTransform(sysy::Function *func);
+    void constantPropagation(sysy::BasicBlock *bb);
+    //bool isConstantValue(sysy::RVInst *inst);
+    //void replaceConstantUses(sysy::RVInst *defInst, int constantValue);
+}; // class ConstProp
+
+} // namespace transform
\ No newline at end of file
diff --git a/src/sysyc.cc b/src/sysyc.cc
index 03b2580..d4bdb50 100644
--- a/src/sysyc.cc
+++ b/src/sysyc.cc
@@ -9,6 +9,7 @@
 #include "backend/llir.h"
 #include "backend/assembly.h"
 #include "opt/peephole.h"
+#include "opt/constprop.h"
 
 struct ArgsOptions {
   std::string srcfile;
@@ -29,6 +30,7 @@ class TransformFlags {
                                        {"--fpeephole", false},
                                        {"--verbose", false},
                                        {"--fparallel", false},
+                                       {"--fconstprop",false},
                                        {"--opt", false}};
   std::string srcfile;
   void parseFlags(int argc, char** argv) {
@@ -57,6 +59,10 @@ class TransformFlags {
       transform::Hole hole(this->module);
       hole.moduleTransform();
     }
+    if (this->flags["--fconstprop"]) {
+      transform::ConstProp constProp(this->module);
+      constProp.moduleTransform();
+    }
   }
   void emit() {
     if (this->flags["--emit-ir"]) {
diff --git a/test/17_constprop.sy b/test/17_constprop.sy
new file mode 100644
index 0000000..556a4a2
--- /dev/null
+++ b/test/17_constprop.sy
@@ -0,0 +1,12 @@
+int main (){
+    int a = 30;
+    int b = 9 - a / 5;
+    int c;
+    c = b * 4;
+    if (c > 10) {
+        c = c - 10;
+    }else{
+     c = 100;
+    }
+    return c * (60 / a);
+}
\ No newline at end of file