Abstract: There are two problems in the performance test and practice use of the Valve Positive Function Hydro-percussion Machine, those are, first the tested blow frequency is lower than the designed, secondly the life of the spring is short. They are caused by that the free vibration frequency of the spring is equivalent to the changing vibration frequency of outside load. This causes the spring resonating, the hydraulic pressure undulating, the work time lengthening and the blow frequency lower. In addition, the safety factor of the fatigue strength of the spring is less than the permissible. This causes the life of the hydro-percussion machine shortening. Improving the valve structure and designing the spring parameters anew can raise the free vibration frequency and the safety factor of the spring.