Recently, the fresh water resource is facing a crisis which is becoming increasingly acute day by day in most countries as well as in China. The contradiction of water supply-demand is the reflection of relationship between water supply and water demand, affected by water quantity, water quality, distribution pattern and exploitation condition, and closely related to the water resource demands of various departments. The contradiction is the result of comprehensive influence affected by a number of natural and economic factors. As we know, the water in nature is limited, and the distributions of water in different place and times are extremely uneven. With the increase of consumption, water resource has become insufficient in many regions. In China the actual total fresh water consumption reached about 470 billion m3 by the end of the 1970's, around 4.7 times the amount of consumption of the years just following the liberation. In cities living consumption of water has been multiplied by 8 times while that of industry (including thermal power) by 22 times. In some regions and cities, the amount of water consumption has already reached the available point of moderate water year. In the slight low water year the supply does not match the demand. And in the very low water year the problem of scanty fresh water would become really serious.From the point view of tapping new sources of water, desalination of sea water should be developed in regions and cities near the sea. But the cost is much high now. For most cities far from the sea, the sea water is unavailable. By way of the water transported across watershed, the water resource can be redistributed among the districts. Of course, this is the one method worth to be paid attention to. But to do so is much complicated; the con is so expensive that it is difficult to practise in very short period. In many regions and cities water supply insufficient, while tremendous waste of water is really existing. And to reduce consumption is a potentiality in daily life and production. So the basic means to mitigate the contradiction between supply and demand of water resources is to reduce consumption. On the basis of overall reducing consumption, vigorous measures should be adopted to tap new sources and to get a reasonable management of water resource.