Abstract: Water resource is the most important material condition for grain production. The economic accounting of water resource is the basis for the management of water resource and the establishment of reasonable price and ordered market. At present, there has no unified and authoritative accounting method for economic value of water resource, needless to say the study on the agricultural water resource in grain production. Based on basic principle of income capitalization approach and the C-D production function, economic value method for accounting of water resource in grain production was established, and Huang-Huai-Hai Region was taken as study case. The results show that the net income of water resource is in order of that in rice production, maize production and wheat production. The average economic value of water resource in grain production in Huang-Huai-Hai Region is 1.02 yuan/m3, and there is a little difference among different regions. In fact, the economic value of agricultural water resource was seriously underestimated.