Abstract:By using the pipeline operator, the pressureflow equation of valve was converted into the one of load. The distributed parameter model and the model of valve controlled symmetrical cylinder hydraulic system were combined to establish the transfer function of the whole system. Bode diagram of the system was drawn by MATLAB programming, and the impact of length and internal diameter of pipe on the quickness and stability of valve controlled symmetry cylinder hydraulic system was obtained. The results show that the increase of pipe diameter and inner diameter will decrease the natural frequency of the system, and the frequency response of the system slows down. The pipeline effect has obvious effect on the high frequency characteristics of the system, the midhighfrequency amplitude characteristic fluctuates, and the phasefrequency characteristic exhibits steplag.