In this paper，we analyze the ecological environment of spring potato late blight from the aspects of the climate characteristics of potato late blight popular occurrence under the background of the existence of the spring potato late blight in Liangshan Prefecture in 2012. The climate characteristics include the warm，cool climate and the rainy，humid season in early summer. We find out the regulation of popular late blight and analyze it in this paper. The epidemic of potato late blight occurrence happens from the middle of May to early July. If the rainy weather reaches 4 days or continuous rainfall continues for more than 3 days，the daily average air relative humidity over 75% lasting 4 to 5 days，late blight epidemic will occur. The conclusion can be used as a warning indicator to prevent and control potato late blight in Liangshan Prefecture in spring，and it also can provide the scientific evidence for the prevention of late spring potato blight epidemic.