Abstract: The decentralized output-feedback disturbance rejection control problem was investigated for a class of uncertain nonlinear interconnected systems subject to high order time varying disturbances. Firstly， the generalized-proportional integral observers （GPIOs） were designed for every subsystem such that the disturbances and unmeasured states can be recovered. Then， based on the estimation information of GPIOs and the output-feedback domination approach， a composite decentralized output-feedback disturbance rejection controller was constructed. The proposed decentralized control scheme can not only handle the uncertain nonlinear interconnected terms， but also remove the influences of the disturbances effectively via feedforward compensation manner. Finally， the effectiveness of the proposed control approach was demonstrated by practical examples.