Abstract: The thermal fatigue crack problem discovered in the pipes of residual heat removal systems was related to the safety of pressurized water reactors. In this paper, the fatigue life of the 304L stainless steel, which was the material of the pipes of residual heat removal systems, was predicted by using the Lagoda-Macha-Sakane’s model in the open-source finite element software Code_Aster. Based on the result of fatigue life prediction, a modified Lagoda-Macha-Sakane’s model was proposed. The thermal fatigue life of the pipes of residual heat removal systems was predicted by using the modified Lagoda-Macha-Sakane’s model. The results show that the predicted thermal fatigue life is consistent with the experimental thermal fatigue life.