Ecosystem services are transferred from the service-providing area to the service-benefiting area to satisfy human needs through some substance, energy or information. Most studies focus on the provision of ecosystem services and few focus on the demands on ecosystem services and their spatial distribution. Here, on the basis of the flow of water conservation services from the providing area to the benefiting area, the benefits produced by water conservation service are investigated and the benefiting areas are identified. The results indicate that in 2010 the water conservation service of key ecological function areas provided irrigation water for 1.67×10⁵ km² of paddy fields and 1.01×10⁵ km² irrigated fields, domestic water to urban residents and industrial water to factories, mines and enterprises of 2.64×10⁴ km² urban construction land and domestic water to rural residents across 3.73×10⁴ km² of rural settlements and formed 6.64×10⁴ km² of inland water which can be used for freshwater aquaculture, downstream regions comprise 1.31×10⁴ km of navigable river, which can be used for inland shipping. The benefit areas of the key function areas located in the upper and middle reaches of the Yangtze River are greater and more influential benefit areas. To protect these key function areas, more attention should be paid to the maintenance and improvement of water conservation. Some benefit areas have access to the benefits produced by water conservation of nine key ecological function areas and cover 17% of the overall benefit area and the length of their channels benefited accounts for 7%. Multiple key ecological function areas should be taken into account equally in the formulation of ecological compensation policies. These research findings can serve as a scientific basis for the compensated use of and ecological compensation for ecosystem services provided by key ecological function areas.