diff --git a/crawler.go b/crawler.go
index 4f81c4f..7fa8b96 100644
--- a/crawler.go
+++ b/crawler.go
@@ -131,28 +131,31 @@ func (c *Crawler) fetchCoverImg(code string) error {
 	imgUrl := strings.ReplaceAll(c.config.GetString("crawler.url"), `*`, code)
 	suffix := filepath.Ext(imgUrl)
 
-	offset := 0
+	startOffset := 0
 	// 如果第一个字符为 '1'，则从下一个字符开始查找
 	if len(code) > 0 && code[0] == '1' {
-		offset = 1
+		startOffset = 1
 	}
 
 	// 获取号码所在的位置
-	index := strings.Index(code[offset:], "00")
-	if index == -1 {
+	splitIndex := strings.Index(code[startOffset:], "00")
+	if splitIndex == -1 || splitIndex+startOffset < 3 {
 		return nil
 	}
+	// 计算原始字符串中的真实位置
+	splitIndex += startOffset
 
 	// 分隔字母部分及数字部分
-	letters := code[:index]
-	num := code[index+2:]
-	if offset > 0 {
-		letters = code[1:index]
+	letters := code[startOffset:splitIndex]
+	numPart := code[splitIndex+2:]
+
+	if len(letters) == 0 || len(numPart) == 0 {
+		return nil
 	}
 
 	fileName := filepath.Join(c.outputPath, fmt.Sprintf("%s-%s%s",
 		strings.ToUpper(letters),
-		num,
+		numPart,
 		suffix,
 	))