The loads and resonant parameters of magnetically coupled resonant wireless power transfer system are changed due to the external environment, then the operating frequency will be random drift and resulting in model parameter uncertainty. To solve the problem of robust output control with uncertain parameters, the H_∞ controller is designed by making use of Robust Control Toolbox of Matlab based on H_∞ control theory in this article. We use the method of structured singular value to analysis robust stability and robust performance for the closed-loop system. The results show that by applying H_∞ controller the closed loop perturbation system realizes robust output control and the controller is designed to provide a general method for such high-order nonlinear uncertain closed-loop perturbation systems.