Abstract: Potato late blight (Phytophthora infestans de Bary)has been a uptrend in recent years in Linxia Hui autonomous prefecture (addr.Linxia) as the production scale of potato for seeds and vegetables was extended quickly, and this disease has become one of the main limited factors in the production of potato in this prefecture.The traditional forecasting method for this disease was usually for the drought mountain area in this prefecture, and its accuracy was very lower when used in the plain plateau area and high humid mountain area in this prefecture. In order to meet the need of potato production,the two linear regression models to forecast the beginningdate of potato late blight (Y) were built, based on the three year survey data in different areas. Y＝9.1699-0.0153X,based on the rainfall in the first ten days of August (X), was very suitable for the drought mountain area, and its forecasting accuracy was 100%. The beginning date of potato late blight (Y) in thehigh humid mountain areawas related close to the temperature (X1) and air humidity (X2) of the first ten days of July, and the forecasting model was Y=13.8180-0.1970X1-0.0403X2 ,with a accuracy of 83%. 

Key words: Linxia, Potato late blight(Phytophthora infestans de Bary), Beginning date, Forecast