HIL (Hardware-In-the-Loop) simulation is one of the key technologies for aerospace devices to imple-ment microgravity simulation experiment on the ground, where the hardware system needs high carrying capacity, high frequency response and high precision control performance. Therefore, a hybrid pneumatic-electric actuator is proposed for the 6-DOF microgravity simulation platform. Each leg of the platform is composed of a cylinder and a servo motor in parallel. The cylinders support 80%-90% of load and the servo motors ensure the high accuracy of the control system. Since the pneumatic force control system is a highly nonlinear system, an integral-linear active disturbance rejection controller (I-LADRC) is proposed. Compared to the PID algorithm, this controller provides a higher precision, faster response and stronger robustness.