This research evaluates the effectiveness of high-resolution PlanetScope satellite imagery in monitoring the impact of grazing on Mongolia's diverse grasslands, a key factor for sustainable agriculture and natural conservation. Conducted from May 2020 to October 2023 at the long-term monitoring sites of Botanic Garden and Research Institute, Mongolian Academy of Science, the study examined sites encompassing both grazed and ungrazed areas within desert, steppe, and mountain grasslands. Integrating ground data such as surface reflectance and geographic coordinates, aims to enhance monitoring accuracy. The satellite-derived Normalized Difference Vegetation Index (NDVI) was chosen as the quantitative indicator. A total of 343 PlanetScope image tiles were utilized and pre-processed for improved radiometric and geometric accuracy using surface reflectance and prepared ground control points. Time series dynamic analysis of the data revealed increasing NDVI differences between grazed and ungrazed areas, indicating potential grassland degradation induced by grazing. The varying rates of NDVI change among different grassland types underscore the importance of effective grazing management for preserving and sustaining Mongolia's grasslands. Furthermore, the strong correlation (0.97) between PlanetScope surface reflectance and field measurements highlighted the utility of this satellite imagery in monitoring grassland dynamics. This study demonstrates the critical role of high-resolution satellite imagery in understanding and managing grassland ecosystems, offering a novel approach to addressing the challenges of overgrazing in Mongolia.