Abstract: In order to reduce the influence of disturbance on the drag-free satellite, a disturbance compensation control combined with optimal control of quadratic performance based on a Kalman estimation theory is presented. Firstly, the relative dynamics of the satellite and the proof mass are modeled. Secondly, the state estimation of the drag-free satellite is given and an optimal controller is established. Finally, the control system with a feedforward loop for disturbance compensation based on Kalman filter is constructed. The simulation results in MATLAB/Simulink indicate that the disturbance compensation together with optimal control is effective to reject external disturbance, the accuracy of the drag-free satellite can be satisfied.