Ok I Got The Solution :

Just Run This SQL Query & Comment Status For All Your Posts Will Be Set ON
PHP Code: 
UPDATE wp_posts SET comment_status='open' WHERE post_status = 'publish' AND post_type = 'post'; 
Matrix4u Reviewed by Matrix4u on . Comment Status Hi .... I am facing some problem with the comment status on my site .. When I actually stated the site, I set comments OFF ... Now after a week, I have set comments ON .... But the problem is, comment box/option is available only for newer posts .... Whereas for the older posts, comment option is still OFF ... Now how to set the comments option ON for all the posts ?? Rating: 5