The relation between the area of potato late blight and weather conditions in Chengde city during 1990 - 2008 was analyzed.It shows that the biological factor p lays a role under suitable weather conditions in the occurrence of potato late blight. Weather conditions such as temperature, p recip itation, relative humidity, sunshine hours are decisive factors for p revalence of potato late blight. The app rop riate temperature, rainy or foggy weather are most conducive to late blight occurrence and p revalence. Using the affected rate as a criteria to classifymeteorological levels for potato late blight, we selected the p recedingmeteorological elementswhich related well to potato late blight as a p rediction factor, then establish the meteorological forecastingmodel using integrated clusteringmethod. Test results showed that the model can imp rove decision - makingmeteorological service level and win time to control the sp read of potato late blight.