Abstract: Extreme weather has a serious impact on the operation safety of urban rail transit. In order to improve the active prevention level of rail transit operation safety, based on the analysis of the "7.20" accident of Zhengzhou Metro Line 5 in 2021, the causes of the accident were analyzed, and the key tasks of urban rail transit flood prevention work and the risks faced in rainy days were expounded. The existing flood prevention measures were sorted out in detail from the aspects of early warning and response mechanism, risk and hidden danger control, emergency treatment and so on. In view of the shortcomings of flood prevention measures, optimization suggestions were given from the aspects of water retaining design, danger perception, joint disposal and so on, which was expected to improve the prevention and control ability of urban rail transit to deal with bad weather and ensure the safety of operation organization.