In order to solve the problem of the forced flow in two cavities of the hydraulic cylinder caused by the active motion of the rudder in different gradient loading experiments of aircraft rudder electrohydraulic load simulator (EHLS), and then leads to surplus torque interference, thus the system structure design based on compound buffer hydraulic cylinder is proposed. For the working principle of the system and the characteristics of hydraulic buffer structure, the structure form of the hydraulic cylinder is designed and the mathematical model is established. The simulation model of the actuator is established through the AMESim simulation software, and the dynamic characteristic experiments are carried out. The results show that the hydraulic cylinder system can not only reduce the mechanical collision during the operation of the piston, and alleviate the forced flow pressure, but also suppress and eliminate the interference of surplus torque. In addition, the load performance of EHLS is improved with high engineering practice value.