The Chishui River Basin is an important ecological security barrier in the upper reaches of the Yangtze River. In view of the prominent contradiction between economic development and eco-environmental protection in the Chishui River Basin, key parameters of normalized vegetation index (NDVI), leaf area index (LAI), surface water content index (SWCI), and land surface temperature (LST) of ecosystem quality in the Chishui River Basin from 2000 to 2018 were extracted based on MODIS data products. The remote sensing ecological index (RSEI) was constructed by ENVI principal component analysis to calculate the ecosystem quality in Chishui River Basin from 2000 to 2018, the trend analysis was carried out by Sen+Mann-Kendall method and the forestland ecological system quality of the Chishui River Basin was compared with the RSEI value under the optimal state of the forest land in Guizhou Xishui Nature Reserve to quantify the restoration potential of the regional ecosystem quality, so as to provide an scientific reference for the ecological restoration of Chishui River Basin and the realization of the important theory that lucid waters and lush mountains are invaluable assets. The results showed that RSEI could well reflect the temporal and spatial distribution of ecosystem quality in Chishui River Basin, and greenness and humidity played a key role in the ecosystem quality of Chishui River Basin. The average value of RSEI in Chishui River Basin was 0.613, and the high value areas were mainly distributed in the humid evergreen broad-leaved forest in the lower reaches, the middle mountain broad-leaved forest and evergreen coniferous forest in the river valley of the middle reaches, and the alpine evergreen coniferous forest and deciduous broad-leaved forest at the junction of Zhenxiong County, Weixin County and Xuyong County in the upper reaches. In the past 20 years, the ecosystem quality of the Chishui River Basin has been mainly improved as a whole, but there was still local degradation, in which the significant improved of ecosystem quality accounted for 6.12% of the total regional area, the slightly improved area accounted for 59.51%, the slightly degraded area accounted for 23.17%, and the significantly degraded area accounted for 1.49%. The difference between the RSEI value and the RESI value of ideal reference system in Chishui River Basin was more than 10% accounting for 49.82% of the total forest area, which mainly distributed in Dafang County, Tongzi County, Bozhou District and some areas of Huairen City and Xishui County.