The invasion of cold air caused a regional strong cooling weather in Chongqing from 13 to 15 March 2011 The significant cooling occurred in the mid west Chongqing, and the heavy precipitation in the mid east Chongqing. Analysis indicates that the temperature and precipitation distribution characteristics are mainly caused by the path of cold air and the occluded front generated in the eastern Sichuan. The turning of the high altitude transverse trough (becoming vertical) guided the north cold air to move southwards. The cold air invaded the Sichuan basin by two paths, the northwest path and the northeast path, when it arrived at the Hetao Region. The cold air invaded the Sichuan Basin by the northwest path, which was the main path of the cold air, caused significant cooling in the mid west Chongqing; the occluded front appeared when the cold air of the two paths met, and its appearance time and location basically consisted with the heavy precipitation. The diagnostic analysis shows that the occluded front region corresponded to the high value region of strong ascending motion and moisture convergence, so it is the main reason for the heavy precipitation in the mid east Chongqing.