Abstract: Based on two methods of evaluating the influence of the coolant environment on the fatigue life of equipment proposed by U.S.NRC in the management guideline RG1.207, the effects on different environmental fatigue correction factor（F_en） expressions and boundary conditions were compared between the NUREG/CR-6909 of USA and JNES of JAPAN. The difference of the environmental fatigue life assessment between environmental fatigue correction factor and environmental fatigue curve was also analyzed. Finally, the three methods were adopted in the analysis of the reactor pressure vessel inlet nozzle fatigue assessment. The methods are Fen method considering strain rate history, environmental fatigue curve method and the Fen method using conservative parameters. The results show that, compared with other two methods, the Fen method considering strain rate history can evaluate the environmental fatigue life of structures with higher accuracy.