Abstract: Ecosystems that depend on groundwater are widely distributed in arid and semi-arid areas. Evapotranspiration (ETG) is a significant component of the groundwater discharge. Water balance methods，experience equation methods and groundwater regime methods are commonly used to calculate ETG. Because the groundwater table record can be easily obtained, it is widely adopted to estimate ETG. It has been proved that the White method incorporates a significant source of errors due to the problematic assumptions. In this paper, an improved White method is proposed. The method was verified using the simulation data. The result indicates that the accuracy is increased by 16%. The improved method was used to estimate groundwater evapotranspiration in the Subeinao watershed using the measured groundwater level. The proposed method plays a significant role in groundwater sustainable development in arid environments theoretically and practically.