Using the data of precipitation in Weihai in winter from 1980 to 1999(Nov.-Feb.), the statistical characteristics of heavy snows are obtained. In these years, there were 21 heavy snows,average 1.0 heavy snows a year. The area of heavy snows is generally smaller, and the possibility of heavy snows over two meteorological observing stations or more is only 0.29. The uneven distribution of heavy snows is in association with the meteorological observing station's location. Most of heavy snows occurred in Wengdeng (average 0.7 heavy snow a year) while the least in Rushan(only one time in these years). The weather systems which caused heavy snows can be divided into two patterns: northeast cold vortex or trough line, and south trough line. The probability of the cold vortex accounts for 95.2%. It is predominant and the vortex caused 20 heavy snows in these years.