diff --git a/ngochess/gtp/util.go b/ngochess/gtp/util.go
index b9e774c..eb83aac 100644
--- a/ngochess/gtp/util.go
+++ b/ngochess/gtp/util.go
@@ -6,13 +6,14 @@ import (
 	"strings"
 )
 
-const alpha = "abcdefghjklmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ" // 无 'I' 的alpha
+const alpha = "abcdefghjklmnopqrstuvwxyz" // 无 'I' 的alpha
+const alphaUpper = "ABCDEFGHJKLMNOPQRSTUVWXYZ"
 
 func Point(x, y int) string {
-	if x < 0 || x >= 50 || y < 0 || y >= 50 {
+	if x < 0 || x >= 25 || y < 0 || y >= 25 {
 		return ""
 	}
-	return fmt.Sprintf("%s%d", byteToString(alpha[x]), y+1)
+	return fmt.Sprintf("%s%d", byteToString(alphaUpper[x]), y+1)
 }
 
 func byteToString(b byte) string {
@@ -20,12 +21,15 @@ func byteToString(b byte) string {
 }
 
 func ParsePoint(pos string) (x, y int) {
-	x = byteToIndex(pos[0])
+	x = byteToIndex(alpha, pos[0])
+	if x == -1 {
+		x = byteToIndex(alphaUpper, pos[0])
+	}
 	y, _ = nmath.Int(pos[1:])
 	y = y - 1
 	return
 }
 
-func byteToIndex(b byte) int {
-	return strings.Index(alpha, string([]byte{b}))
+func byteToIndex(str string, b byte) int {
+	return strings.Index(str, string([]byte{b}))
 }