[Objective] The temporal and spatial variation characteristics of grassland in the Kherlen River basin were analyzed, and the change laws of grassland in China and Mongolia were compared in order to promote the protection and construction of the local ecological environment and to provide a scientific reference for the sustainable development of cross-border grassland.[Methods] Information was extracted from a series of Landsat images based on object-oriented and random forest classification methods to obtain five-phase land cover data for the Kherlen River basin form 1980 to 2020. Grassland changes and the driving factors of grassland change on both sides of the China-Mongolia border were compared and analyzed by means of a grassland dynamic attitude model, a grassland change transfer matrix and a centroid model.[Results] ① Grassland in the Kherlen River basin declined from 1980 to 2020. A total reduction of 486 km² was found, where grassland on the Chinese side increased by 130 km² (0.88%). The transfer of bare land was the main reason for the increase in the grassland area. The Mongolia side decreased by 616 km² (0.61%), as grassland was mainly converted into bare land and cultivated land. ② The grassland centroid in the Kherlen River basin moved 1.6 km northeast due to the loss of grassland in the middle and lower reaches of the Kherlen River.[Conclusion] The loss of grassland in the Kherlen River basin was the result of the combination of natural and human factors. From the perspective of grassland area transfer, human activity was the direct cause of its grassland loss.