Abstract: 【Objective】To protect plants from attacks of bacteria and fungi, there is a need to accurately control spray operation under complex agricultural and forestry environments. To solve the major problem are that the parameter of a traditional proportional integral differential( PID )controller is not self-adaptive to the position error, and the hybrid fuzzy-PID controller with coupled rule(HFPIDCR)is difficult to plan in it’s switching scheme in electro-hydraulic actuator(EHA)system of the sprayer chassis.【Method】The geometric, physical and mathematical model of the EHA system were developed. Structural static analysis and optimization design were performed with the finite element method. An underlapped three-position four-way proportional valve was selected as the control component and a fuzzy PID controller was designed. The controllers were established and simulated with MATLAB/SIMULINK. Control effects of three kinds of controllers were compared.【Result】If the two horizontal axis diameters of chassis are increased by 10 mm while cylinder and piston rod diameters of EHA are increased by 5 mm respectively, then the maximum deformation of the horizontal axis and EHA are reduced to 4.6 mm and 1.1 mm respectively. The chassis supporting strength requirements are satisfied. The rising time, settling time, integral absolute error(IAE)and integral time absolute error(ITAE)of the fuzzy PID controller are 0.099, 0.251, 0.013 and 0.005 s in upward motion and 0.088, 0.267, 0.009 and 0.013 s in downward motion, respectively. Comparing to the traditional PID and HFPIDCR controller, the proposed fuzzy PID controller has better comprehensive characteristics and the various control index values are significantly lower. 【Conclusion】The fuzzy PID controller has more rapid response and higher control accuracy in the position tracking control of EHA system of a sprayer chassis.