［Objective］To explore the impact of large-scale ecological projects on the dynamics of grassland vegetation cover，and to elucidate the constraining effects of vegetation changes on ecosystem services，in order to provide a reliable scientific basis for the sustainable development of the region and the improvement of ecological restoration projects.［Methods］Taking the Xinjiang region，which is located in the arid zone，as an example， trend analysis was used to explore the impact of ecological restoration projects on vegetation cover. Based on the InVEST model and the CASA model，four grassland ecosystem services，namely，water production，carbon storage，soil conservation，and net primary productivity（NPP），were evaluated to reveal the constraining effects of vegetation cover on these services under ecological restoration projects.［Results］1）Driven by ecological restoration projects， 79.2% of regional grasslands showed positive normalized vegetation index （NDVI） residuals，and there was a fluctuating increase in grassland vegetation cover. 2）Grassland ecosystem services in Xinjiang region showed an overall upward trend. Water production and soil conservation services reached their maximum values in 2010，and then decreased，with the high-value areas clustered in the Yili River Valley and the northern side of Altai Mountains. Carbon storage and NPP services showed an increasing trend，with uniform spatial distribution of high-value areas. 3）Three constraints between vegetation NDVI and the four ecosystem services were presented as left parabolic，humpbacked，and right parabolic，respectively. The thresholds between vegetation NDVI and Carbon storage service and NPP were 0.49 and 0.35，respectively.［Conclusion］NDVI of the grassland vegetation in the growing season has shown an increasing trend，and grassland ecological restoration projects have significantly improved vegetation cover from 2000 to 2020. When vegetation cover to ecosystem services threshold reaches 0.3-0.5，grassland integrated ecosystem services can be the optimal. Future ecological restoration policies can be improved based on regional grassland vegetation cover thresholds.