In this paper a contrastive analysis on two torrential rains (August 2, 2009 and July 13, 2011) of mid-summer in Jiangsu is presented with Micaps products, automatic station data, Changzhou Doppler radar observations and NCEP analysis field. Research includes precipitation, circulation background, characteristics of radar observations, dynamic and thermal conditions, etc. Result shows that simultaneous reinforement of subtropical high and continental high in a saddle pattern leads to concentrative precipitation and heavy convective motions, rain center locates in the south of low shear, in the north of surface convergence, and near the peak of water vapor transportation over east China. Weak subtropical high contributes to sustaining water vapor transport for easterly wind of tropical system, to weak convection and longer duration of the convection, with the cooperation of meso-scale trigger system at low levels, it makes local rainfall more powerful and makes precipitation center closer to the starting point of water vapor transportation over east China.