In order to achieve stable,accurate and reliable vertical loading of ultra-large force,taking a 80 MN compression-shear testing machine as the object,the mechanical structure,hydraulic system and control system of the vertical loading device were designed.The mathematical model of the position-pressure double closed-loop PID control algorithm was established,and the fuzzy PID controller was designed.Finally,the control system was coupling simulated through AMESim-Simulink,so as to obtain the time domain response curves of displacement and force;and the vertical loading test was carried out on the 80 MN compression-shear testing machine,so as to verify the reliability of the control system.The results show that based on the vertical loading fuzzy PID control system,the steady state is reached at 220 s and both the displacement error and the force error are less than 0.05%,so that the stability,the accuracy and the reliability of the control system are verified.