Abstract: To solve the problem that the picking head of cotton picker could not adjust automatically according to the fluctuation of the ground height in time, a ground height adjusting device for the picking head of cotton picker was designed. The key components of the device was composed of copying mechanism, lifting mechanism and hydraulic control system. Through theoretical analysis, the maximum thrust of the hydraulic cylinder in the whole process of motion was 62 288.56 N, and the parameters of the hydraulic system were obtained according to the motion conditions of the lifting mechanism. The model of the lifting mechanism and the hydraulic system of the height adjustment device was established based on the AMESim simulation software. After the simulation, the flow, displacement, speed, the force of piston rod and the motion characteristics of the lifting mechanism of hydraulic system of the height adjustment device of picking head were analyzed. The results show that the simulation results are consistent with the theoretical analysis to meet the requirements of the height adjustment of the picking head, and the accuracy of the theoretical calculation is verified.