| Using the monthly mean rainfall data during 1960 to 2009 from typical hydrological station in Qujing City, Yunnan Province, calculated the multi time scale standardized precipitation index（SPI） and analyzed the temporal and spatial change characteristics of drought distribution and drought grade in recent 50 years in Qujing City. On this basis, using the rescaled range analysis method (R/S) calculated the Hurst index and researched the rule of drought disaster in Qujing City. The research showed that: The Qujing City was the drought frequently occurred region, in whole year at least one-third of the months will been occurred different degree drought disaster. The H values at different time scale of SPI index were total greater than 0.5. It explained that the drought disaster in Qujing City had long period memory, and the greater time scale, the stronger long term memory. Therefore, the overall trend of drought in future in Qujing City will be associated with the past characteristic, had the self similarity and the cycle of drought disaster was 15 to 17 years. It was the basic consistent with the actual situation in the Qujing City. |