A decentralized variable structure model following controller is designed for a class of uncertain nonlinear large-scale systems with interconnections whose upper bounds have the form of polynormials. Without a priori knowledge of the upper bounds of unknown parameters, interconnections between subsystems and extemal disturbances, the stability of the closed-loop large-scale system is guaranteed by adaptive laws. Furthermore, the sliding mode of each subsystem exists and is reachable. Theoretical analysis and simulation results show the effectiveness of the controller.