Abstract: By means of comprehensive analysis of the main weather situation, effecting system, physical fields quantity, satellite cloud image and radar echo evolution of rainstorm weather process in the summer of 2012, it concluded that the key to local heavy rain was eastward shift and deep and slow moving of Lake Baikal cold vortex;The existence of low level jet stream was the role of increasing precipitation; the windward slope water vapor convergence caused rainstorm weather because of the Greater Khingan Range terrain blocking.