Abstract: Based on measured data from 1971~2017 in 17 national meteorological stations in Liangshan Yi Autonomous Prefecture,the monthly,seasonal and annual standardized precipitation evapotranspiration index (SPEI) for Liangshan and its affiliated counties were counted according to Penman-Monteiths model.The spatial and temporal evolution characteristics of SPEI were also analyzed,and the abrupt M-K test of SPEI was carried out on the representative of Xichang Meteorological Station in this study.The results showed:(1) The degree of drought could be reflected better by SPEI in Liangshan;(2) The interdecadal changes of drought in Liangshan were obvious;the drought were generally in 1970s,1980s and the 10s of the 21st century,relatively humid were happened in 1990s and 2000s;(3) The spatial distribution of drought frequency in Liangshan was uneven.The frequency of drought in the central region was higher than that in the northern and southern regions.(4) The drought in Xichang has been relatively light in the past 30 years,and the last dry-wet mutation occurred in 1987.(5) The last change point from dry to wet was in 1999 in winter,1996 in spring,1994 in summer and 1991 in autumn,showing a trend of advancing seasonally.