Abstract:[Objective] The surface water area changes in various cities of Inner Mongolia Autonomous Region were studied, and the correlation between the changes and natural factors and human activities was analyzed， in order to provide a basis for ecological environmental protection and restoration research and water resource management in Inner Mongolia. [Methods] Firstly, normalized difference water index (NDWI) was determined to extract surface water distribution range. Secondly, the initial threshold was determined from statistics of the spectral indexes of seven surface feature types. Finally, the surface water of Inner Mongolia during 2009—2018 was extracted under the optimal threshold, and the spatial and temporal variation characteristics and influencing factors were analyzed by statistical area. [Results] From 2009 to 2013, the surface water area of Inner Mongolia increased continuously (slope=247 km2/year); from 2013 to 2015, the surface water area decreased sharply (slope=150 km2/year); in 2018, the area rose to the highest point. During the study period, the change law and trend of the surface water area and the natural or human factors affecting the surface water area were different for different league (cities). [Conclusion] The variation of annual precipitation and of river runoff was one of the main reasons for the variation of surface water in some Inner Mongolia League cities, such as Alxa League and BayanNur City. Construction of reservoirs, landfill of rivers and cultivated land were the main causes of surface water changes in some cities, such as Wuhai City, Hohhot City, and Xilingol League.