Abstract: Aimed at improve the output power of the direct-drive wave power system under irregular excitation force,improve the capturing ability of wave energy and reduce the main loss of the system,combining the motor and hydrodynamic equations to build the mathematical model of the direct-drive wave power system. The energy functional was constructed based on the Variational method,and the optimal control law was obtained after solving the extreme value of the functional. Designing the Extended Kalman filter observer to observe the dependent state variables which are difficultly obtained by the system,and the coefficient of the penalty term of the functional is adjusted off-line to obtain the ideal reference current without increasing the overall computational burden. The Field Oriented control strategy is applied to track the ideal reference current,and the relationship between electrostatic force constraint and power capture is considered. The simulation results show that the proposed strategy has fast response and high observation accuracy,which can validly add the power capture capability,decrease the main loss of the system and add the output power.