Drought index analytical methods based on the relative moisture index were used to study temporal variation,spatial distribution and sub-regional evolution characteristic of drought in southwest China using meteorological data from 1958 to 2012. The results show that the average drought area in recent 55 years covers 30% of the total area in southwest China.Some regions on the West Sichuan Plateau,Southwest Sichuan Upland and north and central regions in Yunnan have a drought appearance frequency of up to 60%. The negative absolute value of the relative humidity index in these regions increased over time and drought intensity increased. Components in most regions of the EOF first modality feature vector are negative,indicating that oscillation phases of drought intensity in most southwestern parts are the same. High load regions of each component are focused in the central part of Yungui Plateau,and this region is the area where abnormal drought would be easier to appear with a higher oscillation intensity and sensitivity among all spatial types. The EOF second modality feature vector field showed an opposed phase character because the,southern part including the Yunnan Plateau and south Guizhou Plateau are mainly influenced by the south Asian monsoon while the northern part including Sichuan,Chongqing and north Guizhou are mainly influenced by the Tibetan Plateau monsoon and east Asian monsoon. According to different modality and spatial distribution of REOF feature vector field,the studied region is divided into four sub-regions. West Sichuan abnormal type had obvious decreased drought intensity and catastrophe point from dry to wet was in 1987. Drought intensity of the North Sichuan abnormal type has increased and the catastrophe point from wet to dry was in 1968. The Yunnan Plateau abnormal type and Guizhou Plateau abnormal type have,a decreasing drought index had decreasing trend with fluctuation,but failed to pass a significance test.