Dither can improve the response characteristic of proportional valve, and the dither frequency and amplitude directly depend on the structure parameters of the valve. Based on opencircuit proportional control valve simulation model, the dithering response of the valve spool and the mechanism of friction hysteresis under dithering were studied to determine the optimal parameter range. The simulation model was established, the dither signal was introduced through the dualduty ratio highfrequency PWM form, the proportional solenoid was modeled with electromagnetic finite element method, and the kinetic equations of the solenoid core and valve spool were established by using the Karnopp friction model. The simulation results show that the established friction model can be used to better characterize the hysteresis phenomena of the solenoid force and valve flow rate; under the dither signal excitation, the valve spool responses with dithering displacement and velocity, and the external friction force shifts from the static friction to dynamic friction, which affects the response characteristics of the spool; the dither frequency and amplitude parameters have an optimal range and are determined by the structural parameters of the proportional valve.