Toevaluatetheeffectoflinkfailureonroutechoiceandnetworkoperationeffi-ciency in traffic network， a sort of link importance ranking method is proposed， which takesthe route redundancy index and travel efficiency index into consideration.In two cases beforeand after the failure of link， the stochastic user equilibrium model based on a feasible andreasonable route set is used to carryout the flow distribution and route search.The flow isonly loaded on a feasible and reasonable route set.Once the route impedance exceeds theshortest path tolerance， the path flow is zero.Finally， we can get the change degree index offeasible and reasonable number of routes and individual travel time consumption before andafter link failure.After the Z-score standardized， the corresponding weight is given and thecomprehensive evaluation value of the importance section is obtained.The test analysis iscarried out by Nguyen-Dupuis network.The results show that the method can simulate thechange ofroadnetwork after link failure.The results can provide theoreticalsupport for traffic congestion control strategy and provide theoretical basis for key section identificationand road closure impact assessment.