Based on the Budyko hypothesis,this paper improved the water-energy balance equation integrating soil water storage variable factors,and verified the adaptability of Budyko hypothesis in the Songhuajiang River basin,and analyzed the spatio-temporal variability of actual evapotranspiration and its driving mechanism.The main results are as follows:(1)taking 1995-2006 as the model parameter calibration period and 2007-2012 as the model verification period,using P-∆S to represent the water supply conditions for land surface evapotranspiration,which indicate that soil water storage variable factors have improved the calculation accuracy of actual evapotranspiration.(2)Under the significance level of alpha=0.1,there is no significant trend in the ET_a of each catchment from 1995 to 2012;the spatial distribution of ET_a gradually increases from the west to the east and has obvious zonality.(3)The spatial variation of the contribution of precipitation to ET_a is consistent with the spatial variation of total contribution of the potential evapotranspiration,precipitation and soil water storage variables to ET_a,which indicate that the water condition of the Songhua River basin is the dominant factor affecting the actual evapotranspiration.