In recent years, urban rail transit projects in China have been flooded frequently, threatening the safety of people's lives and property. The Ministry of Transport added "special demonstration report on flood control of engineering projects" to the Administrative Measures for Safety Assessment before Initial Operation of Urban Rail Transit revised in July 2022 as one of the preconditions before the initial operation of new rail transit lines. Therefore, it is necessary and urgent to carry out research on flood prevention capacity of urban rail transit projects. This paper studies the key factors that affect the flood prevention ability of urban rail transit projects from the aspects of external risk, basic flood prevention ability, flood prevention early warning ability, emergency rescue ability, etc., constructs the evaluation index system and its weight coefficient by using expert scoring method and analytic hierarchy process, and proposes the scoring rules for each index according to the current laws, regulations, standards and specifications of China, and puts forward the evaluation method for the flood prevention ability of urban rail transit operation lines. Finally, it is expected to achieve the purpose of providing technical support for the operation safety of urban rail transit in flood season in China.