Based on the scope of change of parameters，multiple sliding mode variable structure controllers were designed for a kind of nonlinear system with uncertain parameters. A switching controller was formed with a given index switching function. Under the guarantee of Lyapunov stability，the controller of system would be switched among multiple sliding mode variable structure controllers according to the switching condition. The mechanism of switching could improve the transient response greatly. A robotic arm was studied as a nonlinear system. Multiple sliding mode variable structure controllers were set up according to the dynamic equation of the robotic arm. An index switching function based on output error was given for the design of switching controller of the robotic arm. To test the effectiveness of the switching controller，four simulation examples according to different scopes of parameter change were investigated. From the simulation，it was concluded that the switching controller could enhance the control performance greatly.