The evaluation of the suitability of urban emergency shelters is very important, and mostly carried out at three indicators: effectiveness, accessibility, and safety. The potential crowdedness of emergency shelters is also an important indicator for evaluating the suitability of urban emergency shelters. It can help relevant departments to reasonably allocate emergency resources and plan and build subsequent emergency shelters. In this paper, we improve the calculation method of the potential crowdedness of emergency shelters from three aspects: Distribution of the Refuge Population, the attractiveness of shelters, and accessibility of evacuation places. The influence of factors such as population size, shelter service capacity, shelter service radius, number of command and evacuation agencies, and the distance decay effect on the potential number of people served by the shelter is taken into account. And quantitatively analyzed the potential crowdedness of each emergency shelter within it, using downtown Shanghai as an example. The results of the study show that nearly two-thirds of the emergency shelters in downtown Shanghai exceed the minimum effective area per capita specified in the code and that the service is highly congested, especially in the three districts of Jing'an, Yangpu, and Putuo, which are the most serious, and need to be appropriately increased to alleviate the service pressure. And there is a serious shortage of emergency places on the east side of Downtown Shanghai to meet the shelter needs of residents. The research methodology used in this paper can reasonably reflect the potential crowdedness of emergency shelters, and provide a reference for the authorities concerned in allocating emergency resources and planning the construction of emergency shelters.