Using MODIS ET data of actual surface evapotranspiration products that were concentrated between 2000 to 2014, we used variable coefficients, the Theil-Sen median trend analysis, Mann-Kendall test, and Hurst index, to investigate the spatial pattern of evapotranspiration, spatial heterogeneity of different dimensionalities, characteristics of time variation, and future trends considering an arid region in Northwest China. The results showed the following: 1) Evapotranspiration over the entire region was very low from 2000 to 2014, and the area of evapotranspiration, less than 200 mm, accounts for 38.329% of the total area. Evapotranspiration decreases from mountainous areas to the plains. Evapotranspiration data were obtained for different land covers, which are forest land, cropland, grassland, and sparse vegetation, arranged from high to low. Mountain forests and grasslands that receive high rainfall have higher values of evapotranspiration (more than 400 mm) than sparse vegetation plains and grasslands that experience low rainfall (less than 200 mm). 2) The degree of variation in evapotranspiration over the past 15 years for the entire region is not obvious, but shows a slight fluctuation. The proportion of areas with slight fluctuations in each subregion ranged from large to small in the order of Northern Xinjiang, Tianshan Mountain, Qilian Mountain, Western Inner Mongolia, Hexi Corridor, and Southern Xinjiang. 3) The degree of variation in evapotranspiration over the past 15 years for the entire region shows changes in the fluctuations with a weakly decreasing trend, at a change rate of-0.9348 mm/a. An analysis based on the pixel scale also shows a mainly decreasing trend. The degree of decreases in each subregion ranged from large to small in the order of Tianshan Mountain, Western Inner Mongolia, Hexi Corridor, Northern Xinjiang, and Qilian Mountain. Only Southern Xinjiang showed an increasing tendency. 4) The Hurst index average of evapotranspiration for the entire region is 0.689. The area of the Hurst index greater than 0.5 accounts for 80.033% of the total area. The trend of changes in evapotranspiration in the future for the entire region is mainly towards a persistent decrease. However, the trend of changes for 22.003% of the area cannot be determined. The future trend of change in the degree of decreases for each subregion from large to small follows the order of Western Inner Mongolia, Tianshan Mountain, Hexi Corridor, Northern Xinjiang, Qilian Mountain, and Southern Xinjiang.