diff --git a/pkg/rpc/jsons/http_cache_config.md b/pkg/rpc/jsons/http_cache_config.md
index 516fe72..631ae1a 100644
--- a/pkg/rpc/jsons/http_cache_config.md
+++ b/pkg/rpc/jsons/http_cache_config.md
@@ -69,7 +69,7 @@
               {
                 "type": "url-extension",
                 "isRequest": true,
-                "param": "${requestPathExtension}",
+                "param": "${requestPathLowerExtension}",
                 "operator": "in",
                 "value": "[\".css\",\".png\",\".js\",\".woff2\"]",
                 "isReverse": false,
diff --git a/pkg/rpc/jsons/http_cache_ref.md b/pkg/rpc/jsons/http_cache_ref.md
index 4ed819b..b742eb4 100644
--- a/pkg/rpc/jsons/http_cache_ref.md
+++ b/pkg/rpc/jsons/http_cache_ref.md
@@ -71,7 +71,7 @@
 					{
 						"type": "url-extension",
 						"isRequest": true,
-						"param": "${requestPathExtension}",
+						"param": "${requestPathLowerExtension}",
 						"operator": "in",
 						"value": "[\".css\",\".png\",\".js\",\".woff2\"]",
 						"isReverse": false,
diff --git a/pkg/serverconfigs/metric_item_utils.go b/pkg/serverconfigs/metric_item_utils.go
index 9918321..ca29084 100644
--- a/pkg/serverconfigs/metric_item_utils.go
+++ b/pkg/serverconfigs/metric_item_utils.go
@@ -86,6 +86,11 @@ func FindAllMetricKeyDefinitions(category MetricItemCategory) []*shared.Definiti
 				Code:        "${requestPathExtension}",
 				Description: "请求路径中的文件扩展名，包括点符号，比如.html、.png",
 			},
+			{
+				Name:        "小写文件扩展名",
+				Code:        "${requestPathLowerExtension}",
+				Description: "请求路径中的文件扩展名小写形式，包括点符号，比如.html、.png",
+			},
 			{
 				Name:        "主机名",
 				Code:        "${host}",
diff --git a/pkg/serverconfigs/shared/request_variables.go b/pkg/serverconfigs/shared/request_variables.go
index 1742707..c5d5fc1 100644
--- a/pkg/serverconfigs/shared/request_variables.go
+++ b/pkg/serverconfigs/shared/request_variables.go
@@ -18,6 +18,8 @@ func DefaultRequestVariables() []maps.Map {
 		{"code": "${requestLength}", "name": "请求内容长度", "description": ""},
 		{"code": "${requestMethod}", "name": "请求方法", "description": "比如GET、POST"},
 		{"code": "${requestFilename}", "name": "请求文件路径", "description": ""},
+		{"code": "${requestPathExtension}", "name": "请求文件扩展名", "description": "请求路径中的文件扩展名，包括点符号，比如.html、.png"},
+		{"code": "${requestPathLowerExtension}", "name": "请求文件小写扩展名", "description": "请求路径中的文件扩展名，其中大写字母会被自动转换为小写，包括点符号，比如.html、.png"},
 		{"code": "${scheme}", "name": "请求协议，http或https", "description": ""},
 		{"code": "${proto}", "name": "包含版本的HTTP请求协议", "description:": "类似于HTTP/1.0"},
 		{"code": "${timeISO8601}", "name": "ISO 8601格式的时间", "description": "比如2018-07-16T23:52:24.839+08:00"},