Abstract: Danjiangkou Reservoir is the core water source of China’s South-to-North Water Diversion Project, and the quality of the reservoir’s ecosystem is a prerequisite to ensure the safe operation of the reservoir and the sustainable northward transmission of “a flood of clear water”. In this paper, by obtaining high-precision and fine-grained ecosystem type of Danjiangkou reservoir area, we construct a remote sensing assessment model of vegetation ecosystem quality based on the ecological parameters such as Fractional Vegetation Cover (FVC), Leaf Area Index (LAI) and Gross Primary Productivity (GPP) to evaluate the vegetation ecosystem quality and analyze its spatial and temporal dynamic changes from 2001 to 2020. The results show that (1) From 2001 to 2020, the vegetation ecosystem quality in the Danjiangkou reservoir area showed a significant upward trend, and the EQI(Ecosystem Quality Indices) in 2001 and 2020 are 56.16 and 78.32, respectively. The increment of vegetation ecosystem quality is higher than 15 in 81.32% of the total area. (2) Ecosystem quality varies among counties (cities and districts); the ecosystem quality index of Xichuan County and Danjiangkou City is lower than the average level of the reservoir area in 2001 and 2020, but the ecosystem quality index has the highest increment, increasing by 25.55 and 23.99, respectively. (3) Among the different ecosystem types, the forest ecosystem quality index is the highest, but the increment is lower. (4) From 2001 to 2020, the ecosystem quality index has a positive correlation with the increase of slope and the increase of ecosystem quality index was the largest in the areas of 0°-3°. When the slope became steeper, the increment of vegetation ecosystem quality raises with increase of slope grade on slopes between 3°-15° and reached the top at slope 8°-15°, afterwards, dropped down. (5) The absolute value of the bias correlation coefficient between ecosystem quality index and precipitation was significantly higher than that between temperature and ecosystem quality index, revealing that the ecosystem quality index was more significantly influenced by precipitation than by temperature. The research results can provide data support for ecological protection policy formulation, ecological protection spatial control and decision making in the Danjiangkou reservoir area, and are of great significance for ecological security and water source protection in the reservoir area.