The rapid development of the network makes online news become an important source of acquiring information. It has a significant impact on the usability of Web sites whether the information published on the Web sites can reflect the current focus of attention or whether the latest progress of the event on the Web sites can be timely updated. In this paper, the clue development trend on the same subject related to the information on Web sites was obtained from the topic clue sentences identified by Conditional Random Field (CRF) model. The time range of topic clues can be inferred by clue development trends obtained, and further the effective range of Web information is estimated. On this basis, combined with the timeliness the information is published and the freshness of the content on Web sites, the timeliness of Web information can be evaluated reasonably. The experimental results show that the proposed method has a good effect on the timeliness evaluation of information on Web sites.