This paper focused on the dual PWM converter and battery of the direct drive permanent magnet wind power generation system. In order to obtain the maximum benefit of wind power system，a capacity optimization model of converter and battery was established. The overall capacity optimization strategy of dual PWM converter and battery was proposed based on nonlinear programming genetic algorithm. The strategy analyzes the benefits of wind power system，the loss energy efficiency，and the costs of dual PWM converters and batteries. An objective function considering national restrictions on the fluctuation of output power of wind field was then established and solved by a nonlinear programming genetic algorithm，which aims at the maximum annual income of wind power system. To verify this strategy，a wind power system was emulated. The results show that，compared with the traditional capacity allocation method，the annual costs of wind power system can be reduced by 10.3%.