Effective control on piston motion speed of valvecontrolled hydraulic cylinder is conducive to improving the working accuracy of hydraulic servo system. A simplified model related to the nonlinear friction force was designed to control the piston velocity of the hydraulic cylinder. The structure of the hydraulic cylinder controlled by a proportional directional valve was analyzed, and the closedloop transfer function of the proportional directional valve was established. Then, through the pressure difference between the two chambers of the hydraulic cylinder, the volume flow equation of the hydraulic medium in the proportional directional valve was calculated. On this basis, the continuous equation of the pressure value of the hydraulic cylinder was obtained, and the fullorder model between the piston velocity of the hydraulic cylinder and the nonlinear friction force was obtained. Finally, in the closed hydraulic circuit, the continuous equation of the hydraulic cylinder pressure value was simplified by the pressure value of the load, and the simplified model between the piston velocity of the hydraulic cylinder and the nonlinear friction force was obtained. In the experiment, the target velocities generated by square wave, sine wave and random excitation signal were tracked and tested. The test results show that the tracking error of this method is reduced by 9.2%, 11.22% and 11.13% respectively compared with sliding mode control method when tracking the target velocity under the conditions of square wave, sinusoidal wave and random excitation signal. It shows that this method can be used to accurately control the motion speed of piston in hydraulic cylinder