As the increasing popularity and complexity of Web applications and the emergence of their new characteristics, the testing and maintenance of large, complex Web applications are becoming more complex and difficult.Web applications generally contain lots of pages and are used by enormous users.Statistical testing is an effective way of ensuring their quality.Web usage can be accurately described by Markov chain which has been proved to be an ideal model for software statistical testing.The results of unit testing can be utilized in the latter stages, which is an important strategy for bottom-to-top integration testing, and the other improvement of extended Markov chain model (EMM) is to present the error type vector which is treated as a part of page node.This paper also proposes the algorithm for generating test cases of usage paths.Finally, optional usage reliability evaluation methods and an incremental usability regression testing model for testing and evaluation are presented.