Abstract: Based on the data of the experiments on seedtime in four sites,namely in Chengxiang with altitude at 1823m,Tuowu with altitude at 2144m,Qingheng with altitude at 1659m and Shangyou with altitude at 2574m,in Mianning County of Liangshan Prefecture of Sichuan Province,and data of the occurrence of the potato late blight,the meteorological causes and the dynamic characteristics of occurrence and epidemiology for potato late blight were analyzed.The results showed that the main period of occurrence and epidemic of potato late blight was from the last ten days of May to beginning of July.During the first ten days of May and the first ten days of June,the potato late blight would occur in five to ten days if the meteorological factors,such as the sequential rainy days lasted more than five days and the relative humidity was higher than 75% in successive six days,which was suggested to be the warning indexes for the occurrence and epidemic of potato late blight.The prevention measures should be taken in five days when these warning indexes were fulfilled.

Key words: Meteorological factors, Meteorological factors, Potato late blight, Occurrence and epidemic, Liangshan Prefecture