Abstract: Decentralized control is an important control scheme for large-scale systems. Local feedback controllers are adopted in stabilizing each subsystems or in enhancing its strength of stability so as to get a overall stable large-scale system. Owing to the inherent power capacity limitation and other conditions of the controllers the control feedback laws become nonlinear ones. The nonlinearity effect on the stability of the large-scale system is studied in this paper. For each subsystem a maximal（in a certain sense）nonlinearity tolerance is given. Then for given nonlinearity tolerances of subsystems the sufficient absolute stability criterion of the overall large-scale system is obtained via aggregation method based on Liapunov functions for each subsystem. The arbitrariness usually inherent in the Liapunov functions is eliminated and in result the Liapunov functions become the best in a certain sense and can offer less conservative absolute stability criterion.