As an important indicator of Web application performance testing - load capacity is a key factor to judge the merits of the Web application performance, load testing model is an important premise to accurately obtain the Web applications load capacity; This article is based on the model of user groups, Through further analysis of the general user behavior , user groups model is been improved properly. The practical application shows that the improved model more realistically simulate real user behavior, and make the data more statistical significance, which can more accurately predict the performance of web applications. Keywords: Web applications, load capacity, performance testing, load testing, model