Abstract: 08 November 10, 2012 to 14, while 08 from west to east in the hulunbuir city appeared obvious snow weather process, this article through to the snow in the process of two concentrated rainfall time analysis, in combination with high and low air circulation situation and the evolution of each physical quantity field, cloud, etc, find out the influence of the main causes of the snow, mainly produce significant snowfall conditions： the advantage of high and low air circulation to cooperate; Sufficient water vapor sources; The low-level shear line produce strong upward movement; Last for a long time snow, in addition, accompanied by the low level jet are snow snow last provides favorable dynamic thermodynamic conditions.