[Objective] Revealing the terrain characteristics of abandoned farmland in mountainous areas is crucial to farmland protection and food security. [Methods] This study takes Wushan County of Chongqing as the research area，uses Landsat TM/OLI and Sentinel-2 data on the Google Earth Engine (GEE) cloud platform, and adopts decision tree and time series NDVI change detection methods. Extract and analyze abandoned land information in the study area from 2017 to 2021.[Results]①From the perspective of time series characteristics, the area of abandoned land in the study area shows an overall upward trend, the increase from 2017 to 2021 is 2123.50hm2, with a growth rate of 19.61%, and the curve shape within the interval shows a "W"-shaped characteristic. Spatially, abandoned land is globally dispersed and locally concentrated. It is mainly distributed along the direction of the water system, significantly concentrated on both sides of the river, and is surrounded by sloping farmland. ②The abandoned land in the study area is distributed differently in different elevation zones and slope zones. Abandoned land is mainly concentrated in elevations below 1000m and slopes within the range of 5°-20°. In areas with an elevation below 1500m, the area of abandoned land and the rate of abandonment show a pattern of "first increasing and then decreasing", reaching the highest point in 2019; in areas with an elevation above 1500m, the area of abandoned land and the rate of abandonment show a pattern of "first decreasing and then decreasing" over time. The law of "increase" reached the lowest value in 2020.③The distribution index of abandoned land under different terrain levels is a continuous decrease type, and the distribution index of terrain gradient 1 and 2 is greater than 1, which is the dominant area of abandoned land.[Conclusion] The combination of decision tree and NDVI time series change detection method can accurately identify abandoned land, and the recognition accuracy is 83.59%. The results of this study can provide reference for other abandoned land in similar terrain areas.