The monthly average discharge variations of Yellow and Yangtze River have been studied from the accumulated data in recent more than 50 years. Some interesting results have been shown that the interannual average discharge in the middle and low reaches of the Yangtze River is about 20 times of that in the Yellow River. The monthly flow of Yangtze River in the early summer (June) is about 50 times of that in the Yellow River. The significant flow of the Yellow River mainly appears from July to October. Comparison with other 8 months, the monthly mean discharge in each of these 4 months is about 14.5% of its total annual discharge, and in each of other 8 months, is only about 5.25%. The river flow of Yangtze River increases from May. The monthly average discharge from May to October is about 12% of its total annual discharge, out of this period, is only about 4.67%. In recent 50 years, the annual discharge anomalies of the lower reaches of the Yellow River was positive before 1968, was about normal from 1969 to 1985 and was negative from 1986. This negative anomalies tendency has been aggravated partly by the human behaviors, especially in the ninety’s, it has resulted in the river flow sharply down and even leaded to interrupt the river flow frequently in the lower reaches of the Yellow River. Comparatively, there were a significant positive anomalies around 1953 to 1955 in the middle and lower reaches of the Yangtze River, after that it slowly decreased, then it was back to increase in the ninety’s. An obvious increase appeared in 1997 to 1999, and was associated with several severe floods in the ninety’s. All the evidences have shown that the Yangtze Rive has more water resource and more stable than the Yellow River. And the water resource in the Yellow River is varied and deficit, especially in the recent decade. So that the South-to-North Water Transfer Project is necessary and is a possible way to solve the water shortage in the North China, especially in the Spring and the early Summer.