Aiming at the problems of flood control safety and sustainable economic development in coastal cities, this paper summarizes the causes of flood events in coastal cities from two aspects of climate change and human activities. Taking Shenzhen as an example, Xili reservoir station in the upper reaches of Dashahe River and Chiwan tide station in Shenzhen Bay were selected as representative stations, and the risk analysis of flood tide combination in Shenzhen City was carried out based on Copula function. The results show that although the combined risk rate of precipitation and high tide level is lower than that of single field value, the urban flood disaster caused by rainstorm and high tide level in Shenzhen City is more serious, and the economic loss and casualties are more serious. In the planning and design of urban flood prevention and drainage, more attention should be paid to the combined risk rate of precipitation and tide level.