Water use efficiency (WUE) is an important indicator to characterize the coupling process between carbon and water cycle in terrestrial ecosystem and can reflect their regulations and interactions. Based on MODIS 8-day composite net primary production data (MOD17A2), evapotranspiration/latent heat flux product data (MOD16A2) and ecosystem type data of Ningxia, the WUE changes in different ecosystems from 2000-2017 were analyzed. We also studied the impacts of two factors, e,g. NPP and ET on the WUE changes at monthly and annually time scales. The results showed that:(1) The average annually WUE of terrestrial ecosystems in the region was 1.03 g·C/kg·H₂O, with the range of 0.55-2.98 g·C/kg·H₂O. The higher WUE levels distributed in the terrestrial ecosystems in north and south of Ningxia province, while the lower WUE levels mainly located in the terrestrial ecosystems in the central Ningxia province. (2) The WUE of different ecosystems varied greatly. The order of WUE value from high to low is water and wetland ecosystem, forest ecosystem, farmland ecosystem, grassland ecosystem, settlement ecosystem, desert ecosystem, and other ecosystem. In the same ecosystem, the higher the vegetation biomass and coverage of the sub ecosystem, the higher the WUE. (3) The WUE has decreased by 0.0141 g·C/kg·H₂O·each year from 2000 to 2017, the monthly change of WUE showed a typical single peak shape during a year with a range of 0.02-2.16 g·C/kg·H₂O in theterrestrial ecosystem. (4) At the annual time scale, there was a significant negative correlation (P<0.01) between WUE and Evapotranspiration (ET) in the terrestrial ecosystem, but had no correlation with net primary production (NPP); at the monthly time scale, WUE significantly positive correlated with ET (P<0.05), and significantly positive correlated with NPP (P<0.01), which is related to the seasonal growth of vegetation in a year. (5) According to the strength of ET and the level of WUE, the characteristics of water use efficiency of terrestrial ecosystem in Ningxia can be divided into four types including low ET with low WUE, low ET with high WUE, high ET with low WUE, and high ET with high WUE. The ecological restoration projects implemented in Ningxia province can not only enhance the vegetation productivity, but also promoted the regional water consumption, which decreased the water use efficiency of the terrestrial ecosystem. The conclusion of this paper could provide scientific basis for water resources utilization and ecological restoration in Ningxia Province in the future.