Based on Doppler Weather Radar data, weather maps and satellite cloudy products, a largescale rainfall on 18 April 2009 in Tianjin is analyzed. The characteristics of Doppler Weather Radar products and the distribution of cloud parameters during this rainfall process are discussed. The results show that：(1) it was a stratocumulus mix cloud precipitation process, affected by the Hetao low trough at 500 hPa and surface cyclones over the YangtzeHuaihe River Valley; (2) the reflectivity of Doppler Radar presented the obvious multiphased characteristic: forming, developing, maintaining, and weakening with the complete wind profiler data; (3) during the MODIS satellite passing time, the effective radius of cloud particles was above 15 μm, and the particle radius with the highest appearance frequency was 25 to 27μm. The area with the maximum atmospheric potential precipitation was consistent with the hourly precipitation of the automatic rainfall station.