A systematic understanding of spatiotemporal changes in fractional vegetation cover (FVC) of the Xinjiang grassland and its drivers serve as a scientific reference for regional ecological restoration and sustainable development. Based on the MODIS EVI data from 2000 to 2023, this study estimated Xinjiang grassland FVC by using the dimidiate pixel model, analyzed its spatiotemporal dynamics with the Theil-Sen trend analysis, Mann-Kendall test and Hurst index method, and explored the driving factors by ridge regression and residual analysis. The results showed that: (1) From 2000 to 2020, Xinjiang grassland FVC experienced an upward trend on the whole, yet a significant decrease after 2020. Spatially, it was distributed as high in the northwest and low in the southeast, and decreasing from mountains to basins. (2) Precipitation and soil moisture affected FVC positively, with contributions of 18.6% and 38.3%, respectively; while air temperature and solar radiation affected negatively, with contributions of 22.9% and 20.2%, respectively. (3) Climate change and human activities contributed 57.2% and 42.8% respectively to Xinjiang grassland FVC with 60.8% of grassland FVC dominated by climate change and 39.2% by human activities. (4) While most grassland types in Xinjiang have FVCs driven by joint actions of climate change and human activities, climatic conditions were dominant drivers of FVC in temperate typical grasslands and temperate desert grasslands, whereas human activities had more influence on FVC in temperate meadow grasslands. This study quantified the dual driving mechanisms of climate change and human activities together with their respective contributions by analyzing the spatiotemporal evolution characteristics of Xinjiang grassland FVC, thus providing scientific support and guidance for optimizing the ecological barrier functions and regulating the vegetation cover in arid zones.