The dynamic characteristics of hydraulic selfservo swing cylinder according to the natural frequency formula of hydraulic system were analyzed. It was concluded that its structure had to be optimized so as to obtain as larger the displacement per radian in working chamber as possible under certain conditions with the purpose of improve the dynamic characteristics of hydraulic selfservo swing cylinder by analyzing the four parameters that affected the dynamic characteristics. Based on that，a structure optimization method of the hydraulic selfservo swing cylinder by using genetic algorithm was proposed. In order to improve the dynamic characteristics of hydraulic selfservo swing cylinder， three equations of state and Simulink model were established, the effect of the four parameters in natural frequency equation of hydraulic selfservo swing cylinder on its dynamic characteristics was analyzed, and the optimal solution and initial value were substituted separately to the Simulink model and analyzed. Simulation results show that: it is right and feasible to study its dynamic response characteristics by using the natural frequency formula of cylinder system, and the system natural frequency formula can also be applied to analyze the dynamic response characteristics of other hydraulic system. As compared with no optimization, the overall system dynamic response speed is significantly improved after using genetic algorithm to optimize the structure parameters of hydraulic selfservo swing cylinder.