Abstract: Grape leaf blight is a physiologic disease in south China.It prevaled widely and harmed seriously.The main symptom is to drop leaves in large scale and to effect its photosynthesis.As a result.the quality of fruit was graetly deteriorated.and the maturity of fruits delayed.The causes of this disease was supposed as follows:the raining season in south China is usually concentrated in Spring and Summer with long duration.When climate turned into high temperature,the roots of grape were not able to suit that ecologic environment in rhizosphere,thus caused an imbalance between absorption and evaporation.The methods to prevent this disease are:to improve the rhizosphere environment of growing roots:to apply more organic manures; to cover the plastic film on the ground; to build good plant form; to spray pesticide; and to suitably control the yields of fruit.