Water resource demand in China is exhibiting a remarkable increase; the amount used for agriculture, industry and urban life is only to increase as its economy expands. Stable water supply will be crucial for China to achieve sustainable development in the coming century. Shortage in agricultural water, in particular, might affect not only the food productivity in China but also the world grain market due to the large food demand for supporting her population. This paper studies the long-term water supply and demand forecasts in China. First it presents a study framework for analyzing the water demand and its long term perspectives. Then water demand in each province is estimated up until 2050 assuming that the present trend will be maintained (BaU scenario). Comparing the results with the data of regional water resource endowment, it is shown that provinces in eastern and north-eastern China are likely to face increasingly serious water shortage problems by 2050.