Experiments and analysis were made on A7 N01 S-T5 aluminum alloy welded joints. Nominal S-N curves and the fatigue strength under different survival rate were obtained through the tension-tension fatigue tests. The hot spot stress,gap stress were obtained by finite element method,and then the fatigue properties were evaluated by using the nominal stress method,hot spot stress and gap stress method. The results showed that the mean fatigue strength Δσ was 45.77 MPa by the tension-tension load fatigue test,and after corrections of two standard plus or minus deviations,the fatigue strength ΔσKwas 39.89 MPa under the 95% reliability. The hot spot stress concentration factor was 1.034 and the hot spot stress fatigue strength was 47.39 MPa. The gap stress fatigue strength was123.03 MPa. The fatigue strength under the gap stress method had the largest value,the value under the hot spot stress method was in the medium and the value under the nominal stress method was the smallest. The nominal stress method was more conservative than the other two but the hot spot stress method and gap stress method both need to evaluate the detailed factors and analyze the stress condition accurately so as to make sure the safety of high-speed trains.