Analyzes the working principle of large steel pipe hydraulic test machine in the changes of project. According to the robustness requirement of the practical work process, takes the advantages of fuzzy control to improve the PID control on the non-linear hydraulic servo system, which doesn't need accurate mathematics model of control object and has good robust, and achieves good effect in production. Meanwhile introduces the design idea and method for two-input and one-output fuzzy control system.