When large-scale client requests for applications in server concurrently, traditional solutions create a thread for every request, which will lead to a serious decline in server performance and even crash. By analyzing the JDK's Executor framework, the paper described in detail thread pool model from the principle of work, core thread pool object, implementation strategy and other aspects, applied the thread pool to a online examination system of three-layer C/S architecture, and gave the server's design framework and implementation code. Through simulation tests, the stability of the thread pool technical in the process of solving large concurrent access is proved.