<p>Quantifying grassland changes and their drivers is essential to ensure the stability of grassland resources in China. We established a research framework with two primary objectives: to evaluate grassland degradation and restoration over the past 30 years, and to quantify the contributions of climate change and anthropogenic activities to these changes across different grassland cover types. The results revealed that despite a net loss of 6.87×10⁴ km² in China’s total grassland area from 1990 to 2020, the proportion of high-coverage grassland increased by 2.45%, demonstrating an improvement in productivity per unit area. Conversion of grassland to cropland was the dominant land change type, with 80.83% occurring in the western part of the Northwest Ecological Region. Although the total degraded grassland area reached 3.33×10⁵ km² during 1990–2020, this degradation was overwhelmingly dominated by the mild level (94.98%), with severe degradation accounting for only 5.02%. A comparison of the periods 2000–2010 and 1990–2000 revealed that grassland restoration became enhanced in the northeastern part of the Qinghai-Tibet Plateau Ecological Region but degradation intensified in the southwestern part. Moreover, mobile grazing emerged as the primary anthropogenic driver of grassland changes. These new findings provide an important scientific basis for adaptable grassland resource protection and grassland-livestock balanced management.</p>