Using the data of Doppler radar and the cloud paramters products retrieved from FY-2E geostationary satellite data and MODIS Polar-orbiting satellite data,this paper analyzes the structure and transformation of cloud and precipitation in the extreme torrential rain process in Beijing on 21 July 2012.It shows that three stages of the precipitation process have different vertical structures of cloud and precipitation.1)In the warm area convective precipitation stage,the precipitation starts with the warm rain process.The rain drops grow quickly with significant coagulation in the warm cloud area,and the warm rain process is important for precipitation.With the development of cloud,the cold rain process is intensified.T-Re analysis shows that cloud droplets grow quickly below -10 ℃ level with significant condensation-coagulation.There is a deep zone of mixed phase above -10 ℃ level,with the top of cloud dominated by ice particles,and cloud water converts to rainfall quickly.2)In the front convective precipitation stage,the liquid MCC(Mesoscale Convective Complex) system with highly organization and low centroid is the main precipitation system with high rainfall intensity.The echo intensity increases quickly at ice-water mixed layer,and the freezing layer is the key area of rain microphysical process.The rain drops grow quickly with significant coagulation in the warm cloud area,but the broken or evaporation is not obvious.3)In the backward front precipitation stage,the ice particles increase quickly at near 0 ℃ level by coagulating cloud water.There is obvious evaporation in the early precipitation process.With the development of cloud,cloud water is less in the warm cloud area,and the rain drops can not grow without effective coagulation.