Abstract: This region belongs to the winter rape zone in the Yangtze River Middle and Lower Reaches.Every year , a serious Sclerotinia Sclerotiorum (Lib) de Bary on rape occurs. The observation over the regularity of the growth and decay system during the period (2001-2002) shows that leaves begin to fall ill in the early March. When the air temperature rises to 15℃ and relative humidity reaches over 80%, the condition rapidly deteriorates. At the end of the early May, the diseased stems quickly increase and come to the climax in the middle May. Plentiful rain and high air temperature in florescence are the leading factors of the serious disease occurrence. Species, sowing period, density ,growth and florescence bring a considerable influence on the occurrence. As for the prevention of the occurrence, on the basis of the ecological prevention, we can stick to the chemical prevention and carry on the pesticide control in the whole process of florescence so as to effectively control the damage caused by the Sclerotinia Sclerotiorum (Lib) de Bary on rape.