Abstract: A method of robust adaptive tracking control for nonlinear systems based on least squares support vector machines(LS-SVM) is presented.The no-linear system inverse error caused by modeling error and uncertain factors is regulated with LS-SVM on-line in order to make the system outputs accurately track the outputs of the reference model.The updating rule of LS-SVM parameters is derived from Lyapunov stability theroy.The stability of the nonlinear system is proved.Simulaton results demonstrate the effectiveness of the proposed method.