Under severe accident conditions with countercurrent natural circulating high temperature gas in the hot leg, surge line and steam generator tubes, SG tubes integrity could be threatened by creep rupture, particularly if cracks are present in the tube walls. In this study, the first step we perform thermal-hydraulic analysis to predict the creep rupture parameter of the tubes in severe accident. The next step we apply the creep rupture models to test the potential for the degraded SG to rupture before the hot leg. Then, the mean of the SG tube rupture probability was applied to estimate large early release frequency in simplified Level-2 PSA model, and the overall LERF (Large and Early Release Frequency) risk due to the Induced SGTR was calculated. In the final step, implementation of severe accident management guidance, such as the RCS depressurization and refilling to SG, is evaluated using PSA approach. It can be found that strategy of RCS depressurization and refilling to SG can mitigate the severe accident process under the condition of high and medium pressure, and reduce LERF effectively.