diff --git a/sm9/bn256/g1_test.go b/sm9/bn256/g1_test.go
index 58db1c9..ac89ce6 100644
--- a/sm9/bn256/g1_test.go
+++ b/sm9/bn256/g1_test.go
@@ -9,6 +9,21 @@ import (
 	"time"
 )
 
+func TestG1AddNeg(t *testing.T) {
+	g1, g2 := &G1{}, &G1{}
+
+	g1.Neg(Gen1)
+	g2.Add(g1, Gen1)
+	if !g2.p.IsInfinity() {
+		t.Fail()
+	}
+	g3 := &G1{}
+	g3.Set(Gen1)
+	if !g3.Equal(Gen1) {
+		t.Fail()
+	}
+}
+
 type g1BaseMultTest struct {
 	k string
 }
diff --git a/sm9/bn256/g2_test.go b/sm9/bn256/g2_test.go
index 74e51d6..d5fb608 100644
--- a/sm9/bn256/g2_test.go
+++ b/sm9/bn256/g2_test.go
@@ -93,6 +93,21 @@ func TestScaleMult(t *testing.T) {
 	}
 }
 
+func TestG2AddNeg(t *testing.T) {
+	g1, g2 := &G2{}, &G2{}
+
+	g1.Neg(Gen2)
+	g2.Add(g1, Gen2)
+	if !g2.p.IsInfinity() {
+		t.Fail()
+	}
+	g3 := &G2{}
+	g3.Set(Gen2)
+	if !g3.Equal(Gen2) {
+		t.Fail()
+	}
+}
+
 func BenchmarkG2(b *testing.B) {
 	x, _ := rand.Int(rand.Reader, Order)
 	b.ReportAllocs()
diff --git a/sm9/bn256/gfp12.go b/sm9/bn256/gfp12.go
index da97314..6b00595 100644
--- a/sm9/bn256/gfp12.go
+++ b/sm9/bn256/gfp12.go
@@ -100,13 +100,6 @@ func (e *gfP12) IsOne() bool {
 	return e.x.IsZero() && e.y.IsZero() && e.z.IsOne()
 }
 
-func (e *gfP12) Neg(a *gfP12) *gfP12 {
-	e.x.Neg(&a.x)
-	e.y.Neg(&a.y)
-	e.z.Neg(&a.z)
-	return e
-}
-
 func (e *gfP12) Add(a, b *gfP12) *gfP12 {
 	e.x.Add(&a.x, &b.x)
 	e.y.Add(&a.y, &b.y)
diff --git a/sm9/bn256/gt.go b/sm9/bn256/gt.go
index 90ab9f4..cab9390 100644
--- a/sm9/bn256/gt.go
+++ b/sm9/bn256/gt.go
@@ -68,15 +68,6 @@ func (e *GT) Add(a, b *GT) *GT {
 	return e
 }
 
-// Neg sets e to -a and then returns e.
-func (e *GT) Neg(a *GT) *GT {
-	if e.p == nil {
-		e.p = &gfP12{}
-	}
-	e.p.Neg(a.p) // TODO: fix it.
-	return e
-}
-
 // Set sets e to a and then returns e.
 func (e *GT) Set(a *GT) *GT {
 	if e.p == nil {