diff --git a/pkg/nazabits/bits.go b/pkg/nazabits/bits.go
index a37f222..9021703 100644
--- a/pkg/nazabits/bits.go
+++ b/pkg/nazabits/bits.go
@@ -55,8 +55,9 @@ func NewBitWriter(b []byte) BitWriter {
 	}
 }
 
+// @param b: 当b不为0和1时，取b的最低位
 func (bw *BitWriter) WriteBit(b uint8) {
-	bw.core[bw.index] |= b << (7 - bw.pos)
+	bw.core[bw.index] |= (b & 0x1) << (7 - bw.pos)
 	bw.pos++
 	if bw.pos == 8 {
 		bw.pos = 0
diff --git a/pkg/nazabits/bits_test.go b/pkg/nazabits/bits_test.go
index 129e8da..7ecb681 100644
--- a/pkg/nazabits/bits_test.go
+++ b/pkg/nazabits/bits_test.go
@@ -121,6 +121,15 @@ func TestBitWriter_WriteBit(t *testing.T) {
 	}
 	assert.Equal(t, uint8(48), v[0])
 	assert.Equal(t, uint8(57), v[1])
+
+	v = make([]byte, 2)
+	bw = nazabits.NewBitWriter(v)
+	bs = []uint8{2, 4, 3, 5, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1}
+	for _, b := range bs {
+		bw.WriteBit(b)
+	}
+	assert.Equal(t, uint8(48), v[0])
+	assert.Equal(t, uint8(57), v[1])
 }
 
 func TestBitWriter_WriteBits(t *testing.T) {
@@ -134,6 +143,11 @@ func TestBitWriter_WriteBits(t *testing.T) {
 	bw.WriteBits(1, 1)
 	assert.Equal(t, uint8(48), v[0])
 	assert.Equal(t, uint8(57), v[1])
+
+	v = make([]byte, 1)
+	bw = nazabits.NewBitWriter(v)
+	bw.WriteBits(3, 1+8+32+128)
+	assert.Equal(t, uint8(1<<5), v[0])
 }
 
 func BenchmarkGetBits16(b *testing.B) {