A reliability evaluation model for competing failure systems is proposed taking into account the nonlinearity of the degradation process and the degeneration-shock dependency， under the premise of consideration for the effective shock magnitude. Firstly， the nonlinear Wiener process is used to describe the performance degradation process of the system. Then， according to the impact of shocks on the system， random shocks are divided into invalid shocks， effective shocks and fatal shocks. Invalid shock will not cause damage to the system. The effective impact on the degradation process will cause the change of degradation amount and the increase of degradation rate. The modified degradation model is used to describe the impact on degradation. For fatal shocks， the non-homogeneous Poisson process is used to describe the sudden failure process. Finally， combining the sudden failure model with the degradation process model， the reliability model of the competing failure system under the effective impact magnitude is constructed.