A hydraulic basic circuit of preventing hydraulic shock was put forward, which arrived the aim of protecting a servo circuit by increasing and decreasing the pressure gradually. The feasibility of its basic principle was analyzed, and then a model of the hydraulic system was established with simulation by using hydraulic analysis software AMESim. The effect of some parameters of key components on the pressure increasing and decreasing rate of basic circuit was analyzed. The results show that the hydraulic basic circuit has the function of protecting the servo system.