The objective of this study is to present the systematic procedure of the fatigue damage estimation and the remaining life prediction for steel railroad bridges based on the concept of equivalent stress range. The identified stress range frequency distribution of each girder of the bridge is obtained from the predefined random test and the rational analysis procedure. The rational values of cut off point and bar width are derived from the sensitivity analysis of the equivalent stress ranges using these factors. It was found that the systematic procedure presented in this study could be applied practically to the fatigue analysis for existing steel railroad bridges.