For the fatigue life prediction of structure metalic W-rings in high temperature and pressure working environment，considering the loads of gas temperature，medium pressure and bolt preloading，the stress analysis and fatigue life prediction of metal seal ring were completed based on the thermal-mechanical coupling method. The results show that the position of the maximum stress is consistent with the minimum fatigue life，both at the outer surface of the wave arc. The seal ring has the highest fatigue life under the condition of gas temperature of 500 ℃ and pressure difference is 0.5 MPa. The method for predicting the fatigue life of metal seal ring is reliable，which provides the reference for the design of advanced metal seal ring.