In order to solve the problem of unstable speed of cotton picking head in the drum of new type cotton picker,the mathematical model of the valve controlled motor system was established by taking the constant speed control system of proportional valve controlled motor as the research object.According to the mathematical model,the second-order auto disturbance rejection controller was designed.Then the disturbance error and unmodeled error of the system were recorded in the total system error,and the state extended observer was designed to observe in real time and compensate directly by nonlinear controller.Then the feedforward controller was designed to compensate the steady-state error.The simulation results show that the compound control effect of feedforward + ADRC is better,the response time and overshoot are significantly reduced,and it has good anti-interference ability and robustness.