Abstract: By using S-band weather radar, 8.6 mm wave-length cloud radar and wind profile radar data, the two heavy rainfalls in June 23, 2011 (hereinafter referred to as the 6·23 rainstorm) and July 21, 2012 (hereinafter referred to as the 7·21 rainstorm), which occurred in Beijing area, are caused by a meso-scale convective system (MCS). Observation results show that the characteristics of linear convection were found in two rainstorms, and its organization mode was classified as parallel stratiform MCS (PS). Such MCSs in the middle and lower reaches of the Yangtze River move to the east or northeast, but these two MCSs move to the east or southeast. However, the PS which affect Beijing during the final stages is moving to the northeast. Millimeter wave cloud radar could observe the morphological characteristics and development of the cloud over the station. The intensity and velocity of the echo show the evolution, internal structure of the cloud and precipitation state. The wind profiler data indicate that similar changes of the wind field existed in two rainstorms. The interaction of the east wind in the boundary layer during its early stages and the special terrain might be one of the factors leading to the heavy rain in that summer, Beijing. Meanwhile, the velocity in low-troposphere increases significantly before rainstorm. The strengthening of low-level disturbances, wind direction shear and the ultra low-level jet are likely to be the causes of heavy precipitation.