Xinjiang is a region with vulnerable eco-environment in western China. It is of significance to carry out eco-environment survey, assessment and timely grasp the ecological status and its changing characteristics for environmental protection. To meet this requirement, this paper developed a Vegetation-Moisture-Temperature Ecological Index (VMTEI) for measuring of region ecology. As an index for assessment of region ecological status, the VMTEI synthesized three important ecological indicators which were frequently used in evaluating ecology. These are greenness, wetness and heat. The three indicators can be represented respectively by three remote sensing indices or components, which are the perpendicular vegetation index (PVI), perpendicular moisture index (PMI), and land surface temperature (LST). Instead of a simple addition or weighted addition of the three indicators, the 3D spatial geometry principle was utilized to compress the three indicators into one to develop the VMTEI for assessing ecological status. The VMTEI of Xinjiang from 2000 to 2018 was calculated and the trend analysis was carried out by Sen+Mann-Kendall method. The results showed that VMTEI synthesized information on vegetation, soil moisture, and heat could well reflect the spatial distribution and temporal change of Xinjiang's ecological quality. The overall spatial distribution pattern of eco-environment in Xinjiang had little change, which is consistent with the distribution of vegetation with the change of latitudinal extension. The mean value of VMTEI in various ecosystems was obviously different. The eco-environment of wetland ecosystem was the best, the mean values of its VMTEI is 0.43, and followed by forest ecosystems. The worst was the desert ecosystem with VMTEI only 0.28. In the past 20 years, Xinjiang's ecological status has been improved overall. The area with obvious improvement of ecological quality status accounted for 2.332%, mainly concentrated in the farmland and settlement ecosystem which distributed in the Tarim River mainstream, Yili River, Emin River, and Tianshan North Slope Oasis Economic Belt. The main reasons of improvement were the construction of the Three-North Shelter Belt, sand management and the increase of urban green space. The area witnessed eco-degradation was 0.430%, mainly located in the wetland ecosystem which distributed in the periphery of the Taklimakan Desert, Bosten Lake, Aibi Lake and scattered in different regions of Xinjiang mainly due to eco-degradation of plain lakes and some reservoirs to human factors and climate change.