Abstract: In order to better recognize formation mechanism of regional rainstorm in northern Shanxi Province, and provide fine forecasting information for disaster prevention and mitigation, based on conventional meteorological data, NCEP reanalysis data and the intensive observation of automatic weather station data, combining black body temperature data of FY-2E meteorological satellite, a torrential rainfall in northern part of Shanxi Province during 20-21 July, 2012 was diagnosed and compared. The results showed that: (1) the rain storm happened in 200 hPa upper-air westerly stablility strengthening, 500 hPa blocking background, low vortex with shear was the main system, low level southwest jet location north of the west was one of the important reasons. (2) The rain area above the troposphere, the lower atmosphere was in the convective instability state, tall strong dry intrusion and low weak northerly wind invasion were important mechanisms for triggering instability in energy release. (3) Analysis of automatic wind field information displayed main trigger systems that had included three patterns, such as mesoscale vortex, mesoscale shear, and mesoscale convergent which caused different precipitation intensity and duration. (4) The negative area of vertical helicity in 500 hPa showed the development and movement of heavy precipitation system. The water vapor vertical helicity, with considerd effect of water vapor, described the dynamical field of the middle-lower troposphere over rainfall region more clearly, and was a good predictor for the area and movement of heavy rain.