The directly driven wave power generation system has simple structure，easy maintenance and high security. The directly driven permanent magnet linear generator（DDPMLG）is studied and the mathematical model for permanent magnet linear generator is established. The optimal power control algorithm is derived based on the control modes of the double freedom degree and the single freedom degree. The control strategy for the generator electromagnetic force is proposed based on the optimal power algorithm:the time period and the amplitude of the wave are used to calculate the optimal electromagnetic force reference as input signals;in the control of the generator electromagnetic force，the vector decoupling control method is applied in the dq rotational synchronous coordination to realize the control of electromagnetic force control of PMLG，which utilizes the capacity of generator sufficiently. Simulation model for DDPMLG is built in MATLAB/Simulink to analyze and compare the two optimal power tracking methods. The simulation results verify the feasibility of the model and the effectiveness of the control strategy.