Abstract: Due to the demand of urban flood control, drainage and non-point source pollution control in China, the proportion of separate drainage system in cities is increasing, and the initial rainwater pollution caused by separate drainage system has become one of the main causes of urban water pollution. Based on the research results at home and abroad, the research hotspots of the initial rainwater pollution in the separate drainage system were analyzed by using the bibliometrics method, and the sources, pollution characteristics, different control measures and reduction efficiency of the initial rainwater pollution in the urban separate drainage system were comprehensively analyzed. The results showed that pipe deposition was a common problem in the separate drainage system in China, and the pollutants in the urban underlying surface and pipe sediment were the main sources of initial rainwater pollution. Source and pipeline sediment erosion were the main reasons affecting the change characteristics of the initial rainwater quality. In addition, the initial rainwater pollution was also affected by various factors, such as rainfall characteristics, the type of underlying surface, the number of sunny days before rain, and air pollution status. According to the pollution sources and characteristics of the initial rainwater, engineering control measures should be combined with non-engineering control measures to carry out comprehensive control from the source, process, end, and laws and regulations, so as to reduce the pollution caused by the initial rainwater of the urban separate drainage system and improve the quality of the urban water environment.