In order to solve the problem that the speed of the hydraulic motor of cotton picking head is unstable and nonsynchronous due to the constantly changing load, the AMESim hydraulic system of cotton picking head was modeled by using AMESim and MATLAB/Simulink co-simulation, and the PID control and fuzzy self-tuning PID control simulation wer carried out under varying loads. The results show that the speed of the hydraulic motor with PID control is more stable and more close to the set value than that without any control. Both fuzzy selftuning PID and PID control can make the speed of the hydraulic motor close to the set value, but the synchronization accuracy of the motor controlled by fuzzy self-tuning PID is higher than that by PID control.