Abstract: The problem of sliding mode control was investigated for a class of MIMO system. A modified exponential approximation law was used to effectively reduce the chattering caused by variable structure control, and the theoretical proof was given. The proposed method was applied to the design of hydraulic looper systems, where the coupling between looper height and tension control were regarded as interference. Simulation results demonstrated the effectiveness of the proposed method. The controller could make the looper systems get better control performance and reach a stable equilibrium state quickly.