Abstract: Considering the physical constraints of float position and velocity in direct drive wave power generation system, a constrained feedback power optimization scheme was proposed based on linear quadratic Gaussian（LQG）. In order to formulate the state space model of the system, the hydrodynamics tools was used to obtain the radiation force data. The standard Kalman filter was used to obtain the full state information of the system to construct the minimum performance index function and calculate the optimal state feedback gain. The sliding mode controller was designed, in which system modelling mismatch losses was compensated. Used Lyapunov judgement, the system stability was proved. Compensate the state deviation and power loss when the system model is mismatched. The feedback gain was calculated off-line and the sliding mode variable structure control parameters were adjusted to reduce the complexity of the control strategy. Simulation results show that the proposed control strategy has good dynamic performance and robustness, can improve the system output power without violating physical constraints.