After a few decades of studies to establish a theoretical basis, the continuum damage mechanics is now finding engineering applications as an effective modeling method to evaluate the damage, fatigue and life of materials. Before applying the method, it is necessary to determine some material parameters to characterize the damage and fatigue behaviors of the material in question. In this study, the material parameters of the rail steel used for the JIS 50kg N rail were determined based on its stress-strain curve and S-N curve. By using these parameters it was demonstrated that numerical analyses could successfully reproduce these curves. As a simple application of the method, the fatigue life of a bar made of rail steel subjected to repeated three-point bending was predicted and compared with the fatigue life obtained experimentally. That the life span values obtained through analysis agreed well with those from experiments shows that the analysis based on damage mechanics is a useful method to predict rail fatigue life.