URL Rewrite Problem

I want to change my search url style.For example when i search something i want to see something like this
xxxx.com/blog/aaaa.html
aaaa is the search word .
I tried it to do it with the code blow. But it doesn’t effect something .
How can i solve this problem ?

RewriteEngine On
RewriteRule ^blog/([^/]*)\.html$ /index.php?s=$1 [L]