The present application provides web information detecting method and system. The method according to the present application comprises: pre-extracting keywords from a web page; storing a corresponding relationship between the extracted keywords and a URL of the web page in a database; obtaining a source file of a web page to be detected; searching the database for keywords that have the same URL as that of the web page to be detected; comparing the searched keywords to the source file information of the web page to be detected; and determining the existence of information of the web page to be detected according to a matching degree. The present application increases the accuracy of web information detection.