The connotation of urban vulnerability to heavy rain and flood disasters is expounded based on the concept of vulnerability. A comprehensive evaluation index system and an evaluation model for urban vulnerability to heavy rain and flood disasters are constructed from three aspects: exposure, sensitivity, and adaptability, including 11 indicators. The criteria for dividing vulnerability levels are determined. Taking Qinhuai District of Nanjing City as an example, for a 100-year return period design rainstorm scenario, quantitative analysis of the indicator values is conducted using the MIKE coupled one- and two-dimensional model. The index of urban vulnerability to heavy rain and flood disasters is evaluated using the constructed evaluation model. A spatial distribution map of vulnerability in the research area is drawn, and the characteristics and causes of vulnerability distribution are analyzed. The results show that the MIKE coupled one- and two-dimensional model can be used to obtain the maximum inundation depth and end-of-period inundation depth in the exposure index. Areas along rivers with relatively flat terrain, low-lying areas in the transportation network, areas prone to water accumulation under overpasses, densely populated areas, high GDP value areas, and areas with high exposure levels such as residential areas and business centers exhibit higher vulnerability.