Abstract: The hourly rainfall data of over 200 automatic weather stations in flood season (from June to August) during 2007-2010 in Beijing, the daily flood circulars released by the Flood Control Office of Beijing associated with the Drought Relief Headquarters, the synthetic risk regionalization indices of rainstorm flash flood in Beijing, and the early warning products of short-range and nowcasting rainfall were used to perform correlation analysis between waterlogging occurrence and precipitation intensity in the same period, and then to derive a critical early warning index of urban road waterlogging. Based on the synthetic risk regionalization index of rainstorm flash flood and the critical early warning index of urban road waterlogging, an early warning model on risk degree of rainstorm flash flood in Beijing had been established, and the early warning service products on risk degree of rainstorm flash flood were developed. Applying the products to the flood season during 2011-2012, it is shown that both the critical early warning index of urban road waterlogging and the early warning model have reasonable skills.