Do you have to remove all low quality content?
 

I don't think so, but you must make a significant effort to add pages that are useful to the users.

I think it's better to remove low quality content of web pages, Because content is more important for a website. Giving more useful content for users is help to rank in search engines.

Yes, i have remove all low quality content of web pages,

It depends what you mean by low-quality content. If it's just poorly written and less interesting, but still has a healthy balance of keywords, you might benefit from hanging onto it (at least until you've got enough high-quality content to push it aside).

If your content is full of harmful backlinks, overly saturated with keywords, etc, then it's got to go! It hurts you page every second it's still up.