Abstract: To reduce the combined impact of wind rain action on the safety of urban rail transit operation on long span bridges, taking the metro carrying section of Nanjing Dashengguan Yangtze River Bridge as an example, a mathematical model for calculating train overturning under crosswind action is established, and the train operation safety under wind rain action is studied. Results show that compared to running on the windward side, the critical train overturning wind speed （hereafter ′critical speed′ for short） is higher when train is running on the leeward side; compared to the scenario of strong wind only, the critical speed on either the windward or the leeward sides is lower under wind rain action, while the reduction on the leeward side is more significant; adding bridge ancillary facilities under action of only strong wind reduces the critical speed, and under combined wind rain action, the impact of adding bridge ancillary facilities on critical speed is less; the critical speed does not change much when train runs on side span and mid span under wind rain action; the increase of rainfall intensity has little effect on the reduction of the critical speed. Therefore, it can be derived that wind speed is the main factor affecting train operation safety under combined wind rain action.