Abstract: The fitting stress amplitude-fatigue life (S-N)curve of Q420D high-strength steel transverse-cruciform weld joint was obtained by fatigue tests (test fitting).The fatigue lives of the cruciform joint were predicted by the co-simulation of ANSYS and FE-SAFE softwares, and then the S-N curve was obtained by fitting (numerical fitting).The results by test fitting and numerical fitting were analyzed in contrast.The effects of current code evaluating the fatigue life of the cruciform joint were analyzed.The results show that the relative errors between the numerical fitted and the test fitted fatigue lives of the cruciform joint were not higher than 3.49%, and the relative error of the fatigue limit was 0.93%, indicating the application of ANSYS and FE-SAFE software co-simulation technique to predicting the fatigue life of the cruciform joint was reliable.The test fitted S-N curve (50% survival probability)was in good agreement with the ANSI code designed curve, while the test fitted curve at 95% survival probability was in good agreement with the DNV code designed curve.When the number of cycles was higher than 2×10⁵ cycles, the EN code could better evaluate the fatigue life of the cruciform weld joint than the ANSI code, and had sufficient safety margins.