Abstract: Fatigue test has been performed to investigate the effect of pre-strain on fatigue strength and fatigue crack initiation of carbon steels. Three kinds of typical carbon steel have been employed as tested materials. Main results summarized in this study are as follows: for the same ratio of pre-strain, fatigue limit increases with the increasing of carbon content, but the effect of carbon content on fatigue limit of pre-strained specimen is less than that of non pre-strained one. For lower pre-strain rate, fatigue limit of pre-strained specimen is lower than that of non-pre-strained specimen, the higher the carbon content is, the more the fatigue limit of pre-strained specimen decreases. For higher pre-strain rate, the renewing or increasing of fatigue limit is caused by the increasing of pre-strain rate.