Abstract: Under the background of the significant increase of extreme predipitation events and rapid urbanization, the frequency of urban flooding disasters caused by extreme precipitation events has increased significantly in recent years, causing not only serious casualties but also induced huge economic losses and social impacts. Studies on disaster-causing hydrodynamic mechanisms and disaster reduction countermeasures can provide scientific basis for urban flood prevention and control. In view of the recent typical urban flood disaster events in China, firstly, the characteristics and the disaster-causing hydrodynamic mechanisms of urban floods, especially for floods in urban underground spaces is analyzed. Secondly, the instability of people and vehicles in floodwaters is one of the important causes of casualties and property losses. In addition, the flood risk of urban underground spaces is very high due to the low-lying feature and special space structure. Finally, three mitigation countermeasures for the current urban flood problems are given, including carrying out basic theory research on the disaster-causing mechanisms of urban flooding, strengthening urban infrastructure construction, and perfecting the flood early warning and emergency plan system, which can provide references for urban flood risk management and prevention in China.