Abstract: Abstract: Aiming at target ET calculation in water resources management model based on R - ET (runoff-evapotranspiration) in Yellow River basin, the paper puts forward calculation method and process. The first step is to formulate scheme set according to water resources in research area. The second step is to calculate the target ET of different sub item using the method such as the distributed hydrologic model, remote sensing estimation model, and the water use quota method. The third step is to evaluate each scheme based on the principle of sustainability, fairness and effectiveness, and to find the best scheme. Ordos is taken as the case study and five schemes were calculated in this paper. Scheme 1 is present situation of water resources utilization, and the target ET is 468.79 mm. Scheme 2 is increasing diverting water from the Yellow River, and the target ET is 450.89 mm. Scheme 3 is decreasing the ground water, and the target ET is 432.95 mm. Scheme 4 is to reduce diverting water from the Yellow River, and the target ET is 406.11 mm. Scheme 5 is a saving water plan, the target ET is 383.27 mm. Then, the scheme 5 is the optimal solutions and recommendations according to comprehensive evaluation. The comparison between Scheme 1 and 5 showed that, with the development of population, economy and society, target ET reduced gradually with the high water-saving measures. The proportion of target ET in cultivated land declined, because water consumption of cultivated land reduced. The proportion of residential and industrial land target ET increased due to the economic development. The second and third industry water demand and ecological water use will increase at the same time. In order to guarantee reliability and accuracy of the area target ET, calculation results of distributed hydrological model and the remote sensing estimation method verified the validity. Two methods calculation error of the area actual ET value is 0.78% and 1.22%, respectively. Target ET determination and evaluation in this study provide references for the next step to implement R - ET water management in the Yellow River basin.