diff --git a/source/_posts/downloads.md b/source/_posts/downloads.md
index 38ea688..003823a 100644
--- a/source/_posts/downloads.md
+++ b/source/_posts/downloads.md
@@ -41,7 +41,7 @@ tags:
 
 [第二次上机讲解.pptx](/~zhaozuohong/resources/Experiment2.pptx)
 
-[第三次上机讲解.pptx](/~zhaozuohong/resources/Experiment3.pptx)
+[第三次上机讲解.pdf](/~zhaozuohong/resources/Experiment3.pdf)
 
 # 其它参考资料