Based on the standardized precipitation index data of 89 meteorological stations in southwest China (Sichuan Province, Yunnan Province, Guizhou Province, Chongqing) during 1961–2010, the probability and interval time were analyzed by employing the theory of run and the Copula function. The droughts with duration less than 4 months and the severity less than 3 account for 80% of all the droughts in southwest China. Drought types are mainly light within a month, moderate within a month, severe within a season and severe within inter-seasons. The frequency of occurring of drought with a duration less than 3 months and the severity less than 1 is higher in the eastern and western areas, and the central region has higher frequencies of occurrence of drought with a duration greater than 3 months and with severity greater than 1.5. Return periods of drought in eastern and western areas are longer than that of central region. More obvious spatial difference appears with longer duration and greater severity. The probability differences of the same drought type in different climatic types are within 0.05, indicating that there is no wide-range fluctuation in the occurrence probabilities of all the drought types as the time goes on.%基于中国西南地区(四川省、云南省、贵州省和重庆市)89个站点1961—2010年的逐月标准化降水指数序列,利用游程理论和Copula函数分析了这一地区不同等级和不同历时干旱的出现概率及重现期特征.结果表明：西南地区的干旱事件多为历时小于4个月、强度小于3的干旱事件；月内轻旱、月内中旱、季内特旱和跨季特旱的概率较大.干旱历时小于3个月和干旱强度为中旱以下的干旱类型多出现在西南地区的东部和西部,而干旱历时大于3个月和干旱强度为重旱以上的干旱类型多出现在西南地区中部.西南地区东部和西部的重现期大于中部地区,且随着干旱历时和干旱强度的增大,重现期空间差异越明显.而且,各气候态下相同干旱类型的概率差值不大,概率波动范围为±0.05,即随着时间推移,各干旱类型出现的概率均未出现较大幅度的变化.
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