In this study, the authors have investigated and compared the effects of roller working and ion nitriding on fatigue properties of eutectoid steel. Five kinds of roller worked and two kinds of ion nitrided specimens were used in this test. The fatigue test was performed using a rotating bending fatigue testing machine to evaluate the fatigue strength of roller worked and ion nitrided eutectoid steel. The fatigue test result shows that roller working is more effective on improving the fatigue strength of the material than ion nitriding. On the other hand, the ion nitriding can much greatly increase the surface hardness than the roller working. In the case of roller working, the fatigue properties are improved by the three main factors which are compressive residual stress, work hardening and fiberized micro-structure.