diff --git a/README.md b/README.md
index 11c96ee..61ba5dc 100644
--- a/README.md
+++ b/README.md
@@ -4,4 +4,4 @@ SCPI viewer for OWON SPM6103 Powersupply/Multimeter
 
 ## SCPI command
 
-- [ ] [OWON SPM SCPI manual](https://files.owon.com.cn/software/Application/SPM_Series_programming_manual.pdf)
+- [ ] [OWON SPM SCPI manual](SPM_Series_programming_manual.pdf)