Based on the daily data of eight meteorological stations in Shiyang River Basin from 1984 to 2019, the temporal and spatial variation of ET₀ was analyzed. A number of qualitative and quantitative analysis methods were combined to examine the correlational relationship between ET₀ and meteorological factors, determine the dominant meteorological elements, and explore the sensitivity and contribution of ET₀ changes to the dominant factors. The results showed that the ET₀ had been increased significantly in Shiyang River Basinand reached the significance level of 0.05 in most areas of the basin. In space, it gradually increased from south to north. The high value area(1 148.89~1 246.91 mm) was located in Minqin County, while the low value area(775.30~864.07 mm) was located in Sunan Yugur Autonomous County of Zhangye City and Tianzhu Tibetan Autonomous County of Wuwei City. The order of seasonal variation of ET₀ was summer (409.35 mm)>spring(303.36 mm)>autumn(184.84 mm)>winter(85.6 mm). Except winter, spatial distribution gradually increased from south to north. The results of cluster analysis and grey relational analysis showed that T (average daily temperature), RH (average relative humidity), n (sunshine duration), P (precipitation) and u (wind speed)were the five key meteorological factors. Path analysis results showed that T was the most important factor,and the role of P could be ignored. ET₀ had different sensitivity to meteorological factors. RH was the most sensitive factor affecting the change of ET₀.The first three factors changed in the same direction with ET₀, while RH changed in reverse direction.The contribution rates were 13.61%, 0.48%, 2.34% and 2.86%, respectively.ET₀ in Shiyang River Basin showed an increasing trend, which was due to the joint action of decreasing RH and increasing T, n, and u over the years. The increase of T was the main reason for the increase of ET₀.