Abstract: Xichuan County serves as a primary water source area for the middle route of the South-to-North Water Diversion Project. Investigating the spatiotemporal variations and driving mechanism of vegetation cover in Xichuan County is significant for the ecological restoration of the county and the environmental protection of the water source area for the middle route. Based on available Landsat and MODIS data, this study constructed long time-series fractional vegetation cover (FVC) data for Xichuan County from 2002 to 2022 using the spatiotemporal adaptive reflection fusion model (STARFM) and the dimidiate pixel model. In combination with regression and trend analyses, the geodetector model, and correlation analysis, this study explored the spatiotemporal variations and driving mechanism of vegetation cover in Xichuan County during the study period. The results indicate that the coefficient of determination (R²) between the STARFM-reconstructed and real annual-scale FVC reached 0.914, an improvement of 0.05 compared to 0.864 under conditions of data missing. Therefore, the STARFM can provide a reliable data basis for more accurately investigating the dynamic evolution of vegetation cover in Xichuan County. From 2002 to 2022, the vegetation cover in Xichuan County was ordinary, with an average FVC value of 0.516, characterized by higher vegetation cover in the northwest compared to the southeast. The vegetation cover in Xichuan County showed an overall improvement trend, with an improved area representing 76.02 %, primarily covering the northwestern and southeastern portions of Xichuan County. In contrast, the degraded area represented 23.98 %, primarily covering the areas surrounding the Danjiangkou reservoir, Danjiang River, and Xishui branch. The spatial heterogeneity of vegetation cover in Xichuan County was predominantly influenced by elevation and slope, followed by soil type and average temperature, with minimal impacts from soil texture and average rainfall. The improvement and degradation of vegetation cover in Xichuan County were principally caused by anthropogenic factors, with minimal influence from climate factors. The primary anthropogenic factor denotes the middle route of the South-to-North Water Diversion Project, which contributed significantly to vegetation growth rather than inhibitory effects.