Abstract: Targeting the problem of effective length of safety line lacks specificity in each line, by analyzing relevant requirement of urban rail transit safety line setting, considering suburban rapid rail transit characteristics, the main factors influencing safety line are analyzed. Taking Dahe Station of Fuzhou Airport Line as an example, the theoretical length of safety line is calculated to be 55.00 m, which is 1.64 meters shorter than that of the actual station. The feasibility of the calculation method is verified.