Dongsheng mining area in Mongolia is located in the middle of Yellow River,with afrailty ecological environment and climate.Under the background of global warming,investigating the variation of surface dry-wet conditions in this region over the past decades is ofgreat importance.Based on the potential evapotranspiration(ET0) calculated by using the Penman-Monteith Method,the ration of ET0and precipitation was used as aridity index(AI).The variationand trend of surface dry-and-wet condition during the year 1957-2012 was studied,the abrupt test,the frequency analysis and wavelet analysis of the time series variation of ET0and AI were alsoconducted.