To objectively and veritably reflect the impacts of water supply benefits in an ecological water supply system and to remedy the drawbacks of traditional indirect calculation methods which are incapable of considering all the benefits, emergy analysis is applied to quantify the benefits of ecological water supply by converting the input and output of the ecological producing system into a unified dimension. The emergy chart of the ecological producing system has been drawn and the energy analysis table has been set up. The benefit sharing coefficient of ecological water supply was calculated based on which the total benefit of ecological water supply and the benefits of pre-stere water were obtained. Beijing-Tianjin-Hebei region, an emergency water supply area in the Eastern Route of the South-to-North Water Diversion Project, was taken as an example to calculate the benefit sharing coefficient of the ecological water supply and the benefits of pre-stere water using the data in 2015. The results are 4. 08%, and 5. 48 yuan/m³, respectively.