The traditional PID controller has a shortage of an-interference performance, parameters setting and time-varying control. In order to improve the output-voltage performance of the inverter and robustness of battery energy storage system power supply, this paper puts forward a control method based on optimized fuzzy PID controller. Based on expounding the definition and math algorithm of fractional order controller, the method introduces fuzzy control rules to adjust the parameters of the controller, meanwhile, combines with the self-learning ability of the neural network to adjust and optimize the controller parameters online by improving the membership function and fuzzy control rules constantly. The simulation results show that the quality of anti-interference and robust of the optimized control system are enhanced, the controller has better construction and dynamic performance, above all, the optimized control methods are feasible for the inverter of battery energy storage system.