diff --git a/sm2/sm2.go b/sm2/sm2.go
index bbd13ff..ff31793 100644
--- a/sm2/sm2.go
+++ b/sm2/sm2.go
@@ -569,12 +569,9 @@ func Sign(rand io.Reader, priv *ecdsa.PrivateKey, hash []byte) (r, s *big.Int, e
 	}
 	maybeReadByte(rand)
 
-	// Get min(log2(q) / 2, 256) bits of entropy from rand.
-	entropylen := (priv.Curve.Params().BitSize + 7) / 16
-	if entropylen > 32 {
-		entropylen = 32
-	}
-	entropy := make([]byte, entropylen)
+	// Get 256 bits of entropy from rand.
+	entropy := make([]byte, 32)
+
 	_, err = io.ReadFull(rand, entropy)
 	if err != nil {
 		return