An advanced sliding mode control with unidirectional auxiliary surfaces was studied together with exponential approach law.Firstthe switching surfaces were designed for nonlinear systemand unidirectional auxiliary surfaces were designed taking state constraints into account.Then a sliding mode controller with unidirectional auxiliary surfaces (UASSMC) was designed based on the exponential approach law.It was noted that the system states would converge to the switching surfaces in a finite timeand the formula of the convergence time was presented.The simulation results demonstrated that:compared with ordinary UASSMCthe controller based on the exponential approach law can effectively suppress the chatteringand has higher convergence speed.