Abstract: Radar-measured products from a S-band Doppler weather radar in southern Beijing,which was installed and put into operation in 2006,are used to analyze the isolated torrential rain which occurred in the morning on July 7,2006 around the Olympic Green(the Olympic Sports Center).They include the element of wind from surface automatic weather stations and automatically detected data by wind profilers and are available every 6 minutes.The result shows that the local heavy rain event with a spatial scale of about 15 km and the temporal scale of 2 hours is a typical example influenced by a thunderstorm cell.The cell causing the heavy rainfall emerges in the topographic echo belt from Mentougou through Shijingshan to Haidian area.The echo belt is composed of several meso-γ-scale mesocyclone echo cells.The research shows that the mesocyclone echo cells generate in the surface layer and it is all related with the development of thunderstorm cells,convergence of surface layer,and dynamic processes bringing about boundary layer disturbance.