Abstract: Based on the meteorological data collected from six weather stations in recent 50 years in Shiyang River Basin, the reference crop evapotranspiration(ET₀) was calculated with the Penman-Monteith equation recommended by FAO in 1998. The change characteristics of monthly and annual ET₀ were analyzed. ET₀ values were decreasing year by year in other regions except Wuwei and Sunan. The average ET₀ values in 1990s were greater than those in 1980s in all stations, which showed that impacts of climate change on ET₀ were large. The correlations of average temperature, average maximum temperature, annual sunshine hours, average wind speed, average relative humidity, annual rainfall, annual evaporation and altitude with ET₀ were analyzed. The coefficient of correlation of ET₀ with average relative humidity was greatest. Spatial variation of ET₀ values was obvious and the value was increasing from mountainous area to oasis plain in Shiyang River Basin.