diff --git a/ets2panda/checker/types/ets/etsUnionType.cpp b/ets2panda/checker/types/ets/etsUnionType.cpp
index 97b5f76d8bd976d910878cb9f7089e0866f5bf64..334e6e705d4467fe182daecf5a03c18a4db59388 100644
--- a/ets2panda/checker/types/ets/etsUnionType.cpp
+++ b/ets2panda/checker/types/ets/etsUnionType.cpp
@@ -245,15 +245,26 @@ void ETSUnionType::CastTarget(TypeRelation *relation, Type *source)
     RelationTarget(relation, source, relFn);
 }
 
+static bool IsStringEnumtypeOf(Type *const super, Type *const sub)
+{
+    if (!super->IsETSStringType() || sub == nullptr) {
+        return false;
+    }
+    if (sub->IsETSStringEnumType()) {
+        return true;
+    }
+    return false;
+}
+
 static std::optional<Type *> TryMergeTypes(TypeRelation *relation, Type *const t1, Type *const t2)
 {
     auto *const checker = relation->GetChecker()->AsETSChecker();
     auto *const never = checker->GetGlobalTypesHolder()->GlobalETSNeverType();
 
-    if (relation->IsSupertypeOf(t1, t2) || t2 == never) {
+    if (relation->IsSupertypeOf(t1, t2) || IsStringEnumtypeOf(t1, t2) || t2 == never) {
         return t1;
     }
-    if (relation->IsSupertypeOf(t2, t1) || t1 == never) {
+    if (relation->IsSupertypeOf(t2, t1) || IsStringEnumtypeOf(t2, t1) || t1 == never) {
         return t2;
     }
     return std::nullopt;
diff --git a/ets2panda/test/runtime/ets/enum_stringEnum_as_union.ets b/ets2panda/test/runtime/ets/enum_stringEnum_as_union.ets
new file mode 100644
index 0000000000000000000000000000000000000000..30308fa30261c5ed78c72cdfb99454f8be732b32
--- /dev/null
+++ b/ets2panda/test/runtime/ets/enum_stringEnum_as_union.ets
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2025 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+enum StringEnum {
+    A = "A",
+    B = "B",
+    C = "C"
+}
+
+class C {
+    public a: string | StringEnum = StringEnum.A;
+}
+
+interface I {
+    a: string | StringEnum;
+}
+
+type UTA = string | StringEnum | number;
+
+function foo(a: string | StringEnum): string {
+    return a;
+}
+
+function main() {
+    let a: UTA = StringEnum.A;
+    let b: string | number = a;
+    arktest.assertEQ(a, b);
+    arktest.assertEQ(b, "A");
+    arktest.assertEQ(foo(StringEnum.B), "B");
+    // class
+    let c: C = new C();
+    arktest.assertEQ(c.a, "A");
+    // interface
+    let i: I = { a: StringEnum.C };
+    arktest.assertEQ(i.a, "C");
+}
diff --git a/ets2panda/test/runtime/ets/implicit_stringEnum_as_string.ets b/ets2panda/test/runtime/ets/implicit_stringEnum_as_string.ets
new file mode 100644
index 0000000000000000000000000000000000000000..87b5880fb62df4b08aafd156a6326f9eb0be0c1e
--- /dev/null
+++ b/ets2panda/test/runtime/ets/implicit_stringEnum_as_string.ets
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2025 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+enum StringEnum {
+    X = "X",
+    Y = "Y",
+    Z = "Z"
+}
+
+interface TestInterface {
+    prop: string;
+}
+
+class TestClass {
+    public name: string = StringEnum.X;
+}
+
+function processString(str: string): string {
+    return str;
+}
+
+function concatStrings(a: string, b: string): string {
+    return a + b;
+}
+
+function main() {
+    let directAssignment: string = StringEnum.Y;
+    arktest.assertEQ(directAssignment, "Y");
+
+    let obj: TestInterface = { prop: StringEnum.Z };
+    arktest.assertEQ(obj.prop, "Z");
+
+    let instance: TestClass = new TestClass();
+    arktest.assertEQ(instance.name, "X");
+
+    arktest.assertEQ(processString(StringEnum.Y), "Y");
+
+    let result: string = concatStrings("Prefix", StringEnum.X);
+    arktest.assertEQ(result, "PrefixX");
+
+    let stringArray: string[] = [StringEnum.X, StringEnum.Y, StringEnum.Z];
+    arktest.assertEQ(stringArray[0], "X");
+    arktest.assertEQ(stringArray[1], "Y");
+    arktest.assertEQ(stringArray[2], "Z");
+}