According to the system of four wheel steering, a nonfragile controller is designed via theory of H∞ control and linear matrix inequality (LMI) method in this thesis. The external disturbance can be suppressed effectively by H∞ control theory. Then, by using Lyapunov function method and matrix inequality converter technique, the sufficient condition of controller is obtained via LMI method. Comparing with the existing research method of controller, the problem of nonfragile that controller has uncertainties are consider in this paper. Finally, the MATLAB simulation experiment shows the validity of the proposed linear matrix inequality of controller.