Abstract: The paper gives an evaluation of the quality and quantity of the water diverted northward from the yangtze Basin. It not only answers the question on the possibility of water supply from the Yangtze Basin, but also studies the practical problem of the diversion. This paper analyzes the magnitude and the quality of the water resources of the Yangtze River and estimates the water Volume provided by the Yangtze Basin in the end of the 20th century. Through evaluation and analysis., much more water can be diverted from the Yangtze in the end of the 20th century, but the optimum scheme of diversion is on the middle stretch, while the diversion on the lower stretch will make the water quality worse before the completion of the Three-Gorge project when the discharge of Datong station is smaller than 13000M³/S.