Abstract: In this article,the spatio-temporal characteristics and causality analysis of precipitation anomalies in November 2011 are analyzed.The results show that the precipitation feature in Hohhot is typical,mainly characterized by the following 3 features： The rainfall feature of Hohhot presents strong extremes and apparent phases,meanwhile the precipitation is mainly concentrated in the middle part of Hohhot,while South and north part is small.In November,the Middle West of Inner Mongolia lies in the flat westerlies on 500hPa height field.During that time,the shortwave trough appears frequently,the southern trough is active and the western Pacific subtropical high lies more westward,which lead to warm and wet flow coming from southwest transporting northward.Corresponding to the east part of Northwest China,the precipitation in south central Inner Mongolia is more than normal.The anomaly of rainfall is caused by a response to the La Nina event which stated in September 2011 and the development and enhancement of La Nina event ever since.