The present application discloses methods and systems for incrementally collecting replies in a forum and belongs to the technical field of collecting network information. The method comprises periodically determining whether there is a newly-established post and a post having new replies in all forum list pages needed to be collected: if yes, extracting a main post and reply information from the newly-established post, and extracting the information of the new replies from the post having new replies. The system comprises a determining device (11) for periodically determining whether there is a newly-established post and a post having new replies in all forum list pages needed to be collected; and an extracting device (12) for extracting a main post and reply information from the newly-established post, and extracting the information of the new replies from the post having new replies. The present application can quickly, accurately and completely collect all main post/replies of a post, so that the drawback that the information of turned pages of a post are missed to be searched or cannot be searched through a general search engine may be overcome.