Abstract: Three kinds of S-N curves including experimental S-N curve,experience S-N curve and standard S-N curve were established by MSC.Fatigue software.The effects of residual stress,average stress and joint shape were considered.And these curves were revised according to the related criterion and used to predict the fatigue life of Q235B cross-shaped welded joint.The results show that,the fatigue damage locations of welded joint is consistent with that of experiment by S-N curve method based on MSC.Fatigue.The deviation is 7.9%-28% between the prediction values of experiment S-N curve and that of standard S-N curve.The deviation is 3.3%-19% between the prediction values of experiment S-N curve and that of experience S-N curve.The prediction values of experience S-N curve are higher than that of experiment S-N curve and that of standard S-N curve is more conservative.