Parallelization of test case generation for Web applications is an effective way to improve the efficiency of test generation. Due to the characteristics of front-back end separation and event-driven of Web applications, the traditional parallelization technology is difficult to be applied to automatic test case generation of Web applications. Therefore, it becomes a challenging task to parallelize test case generation for Web applications. In this study, parallelized computing is introduced into the test case generation for Web applications based on GA. By means of the design of thread pool and scheduling logic, the management of the multi-browser process and the acquisition of the path coverage of back end code, the parallel execution of individuals on multiple browsers and the parallel computation of fitness values based on the back end path coverage are realized, making test case generation more efficiently. The experiment results show that compared with GA serialization test case generation, the proposed parallelization method can make full use of system resources and greatly improve the efficiency of test case generation for Web applications.