In order to improve the credibility of the damage degree evaluation to the aviation network due to cascading failures caused by emergency， considering the redundancy ability of airport nodes for the load， which means if the overload occurs in a certain spatial range， the node will not fail immediately but has a certain overload handling ability， an aviation network cascading failure model was proposed based on overload condition and failure probability. Firstly， the overload coefficient， weight coefficient， distribution coefficient， and capacity coefficient were introduced into the traditional "load-capacity" Motter-Lai cascading failure model. Then， the redundant capacity characteristics of network nodes were described by overload condition and failure probability， and different load redistribution strategies were applied to the failed and overloaded nodes to make the model more consistent with the aviation network reality. Theoretical analysis and simulation results show that increasing the overload coefficient within a certain range helps to reduce the impact of cascading failures， but the improvement effect is not obvious after increasing to a certain degree； with the optimal intervals for parameters of the model. the aviation network can maintain better robustness while spending smaller construction cost， and the optimized allocation of aviation network resources can improve the network’s resistance to cascading failures.