Abstract: Traditional resonance methods can be used to improve the operational performance of direct-drive wave power generation systems, but it may be counterproductive under irregular excitation, so an improved impedance-matching control strategy was proposed.Based on the equivalent circuit model, the maximum power capture condition was constructed. In order to adapt to the actual working conditions, a constraint handling mechanisms was proposed. To ensure safe operation of system, the float speed and displacement were adjusted by changing the gain. Taking the excitation force and electromagnetic force as unknown inputs, a sliding mode observer was designed to detect wave force. The control motor tracked the ideal trajectory to achieve power optimization control. The simulation results show that the sliding-mode observer has high accuracy, which can estimate the excitation force online. The proposed strategy can balance the float motion state and output power, and improve the system wave energy extraction.