diff --git a/smx509/equal_test.go b/smx509/equal_test.go
new file mode 100644
index 0000000..70d4319
--- /dev/null
+++ b/smx509/equal_test.go
@@ -0,0 +1,39 @@
+package smx509
+
+import (
+	"crypto"
+	"crypto/rand"
+	"testing"
+
+	"github.com/emmansun/gmsm/sm2"
+)
+
+func TestEqual(t *testing.T) {
+	private, _ := sm2.GenerateKey(rand.Reader)
+	public := &private.PublicKey
+
+	if !public.Equal(public) {
+		t.Errorf("public key is not equal to itself: %q", public)
+	}
+	if !public.Equal(crypto.Signer(private).Public()) {
+		t.Errorf("private.Public() is not Equal to public: %q", public)
+	}
+	if !private.Equal(private) {
+		t.Errorf("private key is not equal to itself: %q", private)
+	}
+
+	enc, err := MarshalPKCS8PrivateKey(private)
+	if err != nil {
+		t.Fatal(err)
+	}
+	decoded, err := ParsePKCS8PrivateKey(enc)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !public.Equal(decoded.(crypto.Signer).Public()) {
+		t.Errorf("public key is not equal to itself after decoding: %v", public)
+	}
+	if !private.Equal(decoded) {
+		t.Errorf("private key is not equal to itself after decoding: %v", private)
+	}
+}