For the study of flood change rule and the relationship with climate change,restoring historical period climate characteristics in Linfen region, through the statistics of the historical data of Linfen City, using the method of mathematical statistics, we analyze frequency of drought disasters, grade sequence characteristics,seasonal and internal variations and the cause during the period from 1840 to 1949. The results show that it happened recorded a total of 54 times, about 2 years per one time, above class Ⅱ proportion was 66.7% , and the drought than half of the total number of drought, it shows that drought damage is serious in the 110 years. The drought frequency of late Qing Dynasty is about 19 % higher than the Republic of China,the level Ⅲ drought is especially significant. They belong to the more drought seasons, and the level Ⅳ drought is relative larger. Most drought season is the whole year drought, spring-to-summer continuous drought, summer drought. Heavy drought and major drought indicate annual precipitation is mostly less than 332.7 mm. The dry cold climate, warm dry climate, El Nino phenomenon and other extreme weather events are background of frequent drought climate. The drastically reduced precipitation is the main reason for the big drought. The prominent contradiction between human and land, land to carry at the forest on the nature of development also contributed to the frequent drought and severe floods.