Abstract: With the increase of population and fast development of economy, the shortage of water resources has become increasingly serious. In this paper, the water demand of China by the mid 21th century has been forecasted based on the macroeconomic model of sectoral water demand projection.The shortage of water resources will still baffle the social economical development of China and the contradiction between water supply and water demand may deteriorate in a considerable long time period in the 21th century.The water shortage peak is predicted to emerge around 2030.The gap between water supply and water demand is hopeful to be slowed down after 2030 and the relative balance between total water supply and total water resources demand will be reached in the mid 21th century.