The sensitivity coefficients of daily reference evapotranspiration (ET_0) to average temperature, wind speed, relative humidity and sunshine hours in the Shiyang River basin during 19592011 were calculated by using PenmanMonteith equation recommended by FAO,based on daily meteorological data provided by the China Meteorological Administer. Moreover, temporal variations of the sensitivity coefficients were analyzed. Results show that relative humidity was the most sensitive factor of ET0 in the Shiyang River basin, wind speed and temperature were in the second place,and sunshine hours had the lowest sensitivity. Because of climate factors contrast and significant spatial difference of the sensitive coefficients,the sensitive coefficient of relative humidity formed high value area in the upstream area of the Qilian Mountains. Meanwhile,the sensitive coefficient of temperature was relatively large. But the sensitive coefficient of wind speed was the largest in the downstream area of the Minqin basin. The sensitive coefficient of sunshine hours had no significant difference in all the areas. The sensitive coefficient of each of the meteorological factors showed a certain degree of volatility. Wind speed was high in winter, but low in summer; temperature and sunshine hours were all high in summer; and the absolute value of relative humidity continued to rise to the maximum in fall. The sensitive coefficient of relative humidity fluctuated in the past 53 years, absolute value showed a significant upward trend, but the wind speed, sunshine hours and temperature had no obvious trend in the last 20 years.