Abstract: The looper system in hot rolling has the features of nonlinearity, strong coupling, uncertainty, and multi constrained. To improve the accuracy and quality of control, an appropriate model ought to be built to realize the decoupling of looper height and tension. By analyzing the dynamic coupling process of looper system and using the mathematical models of hydraulic cylinder and servo valve, a dynamic mathematical model of hydraulic looper system was built at the vicinity of the working point. The control strategy of sliding mode variable structure for a multivariable system was introduced to decouple the system and improve control effect. Simulation results show the effectiveness of the algorithm and the better control effect of the looper control system after decoupling.