替换您的code这一点：

Replace your code with this:

Options +FollowSymLinks -MultiViews
RewriteEngine On
RewriteBase /

RewriteCond %{HTTP_HOST} ^(www\.)?olddomain\.com$ [NC]
RewriteRule ^oldfolder/(.*)$ http://newdomain.com/newfolder/$1 [L,R=301,NC]