Reference crop evapotranspiration (ET₀) is often used to evaluate the capacity of atmospheric evaporation in the terrestrial hydrology cycle. Simulations with climate models and atmospheric general circulation models have shown that changes in meteorological factors affect ET₀. The Mu Us desert is located in the arid and semi-arid region of northwest China, which experiences severe water shortages. To better understand the ET₀ spatio-temporal distribution characteristics in the Mu Us desert, the Penman-Monteith equation recommended by the FAO in 1998 was used to calculate ET₀ at typical meteorological stations, as well as the overall Mu Us desert ET₀, based on 60 years of daily meteorological data (1955-2014). A Mann-Kendall trend test was used to determine the ET₀ spatio-temporal distribution characteristics. Furthermore, a Co-Kriging interpolation was used to draw ET₀ maps, which presented a clear spatial distribution of ET₀ in the Mu Us desert. In addition, a sensitivity analysis was used to analyze the causes of ET₀ change. Annual average ET₀ was 1048.81 mm for the past 60 years. There was a slight increasing trend in the inter-annual variation. The trend of annual ET₀ showed a single peak curve, with the highest value in June (5.77 mm/d), and the lowest value was in January (0.54 mm/d). The average summer ET₀ was 5.23 mm/d, and average winter ET₀ was 0.70 mm/d. Spatially, ET₀ decreased gradually from west to east, ranging from 1058.53 to 1103.85 mm in the west, and from 1014.05 to 1043.44 mm in the east. The sensitivity analysis indicated that ET₀ was positively related to wind speed, air temperature, and solar duration, but negatively related to relative humidity. Furthermore, ET₀ was most sensitive to changes in wind speed, then solar duration, air temperature, and relative humidity, respectively. Seasonally, ET₀ was more sensitive to solar duration in spring and autumn, but more sensitive to relative humidity in summer and winter. Wind speed was the dominant controlling factor on ET₀ in summer, but in spring, autumn and winter, it was air temperature. Overall, air temperature was the dominant controlling factor on annual ET₀ in Mu Us desert. Spatially, ET₀ was more sensitive to temperature in the southeast region of the Mu Us desert, to relative humidity and solar duration in the northwest region, and to wind speed in the south. The spatial distribution of ET₀'s dominant controlling factor was different from its sensitive coefficient. Wind speed was the dominant controlling factor on ET₀ distribution in southwest of Mu Us desert, and air temperature in east. The meteorological factors here were considered dominant in controlling the spatio-temporal variations of the Mu Us desert ET₀. However, advection variation caused by wind speed, temperature and relative humidity, inter-annual variation of the atmospheric circulation, surface uniformity, and human activities, also influence ET₀ in China's arid and semi-arid region. Therefore, the results presented here only reflect the meteorological variables that were included in the analyses. More comprehensive hydrological studies are therefore required in the future.