Abstract: Fatigue cracks appeared in a weld on a transverse shock absorber seat of a railway vehicle during service. By using the fatigue load spectrum, the numerical simulation calculation of fatigue life of cracked welds is carried out by using the nominal stress, hot spot stress and structural stress method respectively. The numerical simulation results show that, the calculation results of the structural stress method are the most consistent with the engineering practice compared with the nominal stress method and the hot spot stress method, and the structural stress method is also obviously better than the other two methods in the identification ability of the stress concentration. Combined with this specific engineering example, this paper further discusses the essential differences of these three methods, and puts forwards a concluding opinion, that is, the structural stress method is most worthy of being popularized in application in the process of anti-fatigue design of welded structures.