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Based on the daily meteorological data of 29 meteorological stations in Gansu province from 1984 to 2019, the temporal and spatial variation of ET0 was analyzed. A variety of qualitative and quantitative analysis methods including principal component analysis, cluster analysis, grey relational analysis, path analysis, sensitivity analysis were organically combined to reveal the internal relationship between ET0 and climatic factors, and to explore the sensitivity and contribution of ET0 changes to the dominant factors in Gansu Province. The results showed that ET0 increased significantly (α=0.05) in Gansu province in recent 36 years and the mutation occurred in 1998.The spatial distribution of ET0 increased from southeast to northwest during the study period. The Gannan plateau was small, while the Hexi plain was large, and the high value of ET0 varied from 1049.3mm to 1260.9mm. Principal component analysis showed that temperature, humidity and radiation had a greater impact on ET0, while wind speed had a relatively small impact. Combined with the results of cluster analysis and grey relational analysis, daily maximum temperature Tmax, relative humidity RH, wind speed u, precipitation P, and sunshine duration n were five key climatic factors. Tmax was the most important factor, and P had the least effect. ET0 had different sensitivity to climatic factors, and RH was the most sensitive. Tmax, n and u had a positive effect, while RH had a negative effect, and the contribution rates of RH, Tmax, n and u were 3.79%, 7.22%, -0.42% and 3.70%, respectively. ET0 in Gansu province showed an increasing trend in recent 36 years, which was due to the combined effects of the decrease of RH and n, and the increase of T and u. The increase of T was the main reason for the increase of ET0. The research results provide scientific basis for the scientific allocation of irrigation water, efficient development and utilization of water resources in this region, and revealing the response mechanism of hydrological cycle-evapotranspiration under climate change. Meanwhile, the exploratory combined application of multiple methods provides a new idea for the analysis of driving factors of ET0 change. [ABSTRACT FROM AUTHOR]