The spatial distribution ET in Gannan grassland was simulated with the energy balance equation and series data sets of data (MODIS and meteorological) from 2000 and 2009. At the same time, the utilization of a modified Penman-Monteith Model simulated the regions average daily potential ET. In accordance with the 55-year temperature changes in the Northwest Arid Region of China, the regions development tendency of remote sensing ET and potential ET were analyzed. It was concluded that the remote sensing ET ranged from 0.981 6 mm to 8.208 1 mm, with a mean value of 5.514 1 mm in 2000. Remote sensing ET ranged from 1.647 2 mm to 7.653 7 mm with a mean value of 5.565 0 mm and potential ET ranged from 1.678 9 mm to 8.248 7 mm with a mean value of 6.158 1 mm in 2009. Remote sensing ET was lower than the potential ET in general. However, remote sensing ET was higher than the potential ET in the Hezuo County, along the Taohe River and around Tieba Township. It explained that there existed a contradiction in the evaporation phenomenon, which was related to the increasing temperature trend of Northwest China. For example, the temperature of 1965, 1982and 1995 increased 6.70%, 11.69% and 7.70% higher than the average of 1957-1998. In particular, the annual temperature of 2010 increased by 57.56%, and its average temperature was 5.77 higher than the average tem- perature of 1957-1998; that is to say, temperature rapidly increased in recent years.