Sensitivity analysis is important in understanding the impact of climatic variables change on the variation of the reference evapotranspiration. In this research, mean daily reference evapotranspirations ET₀ during growing season in 1988-2007 in Ejina oasis are calculated based on FAO56 Penman Monteith model and climatic data, and the sensitivity coefficients of ET₀ to major climatic variables, including air temperature, wind speed, relative humidity and shortwave radiation are calculated too. Results show that the sensitivity coefficients of ET₀ to the major climatic variables in Ejina oasis fluctuate significantly during growing season, and the sensitivity of  ET₀ to shortwave radiation is the most obvious, followed by air temperature, wind speed and relative humidity. According to this study, the response of  ET₀ variation to variation of air temperature, wind speed, relative humidity and shortwave radiation can be predicted with high reliability by sensitivity coefficients.