This paper discusses the definition and connotation of requirement rate of ecological water demand, analyzes the ecological water demand in the middle and lower reaches of the Hanjiang River. Then this paper calculates the effect of the middle line of South to North Water Transfer Project and the Yangtze River to Hanjiang River Water Transfer Project after being completed on the satisfactory degree of ecological water demand in the middle and lower Hanjiang River by long series data calculation. The computed results show that the South to North Water Diversion Project will reduce the satisfaction degree of ecological water requirement in the middle and lower reaches of the Hanjiang River. The Yangtze River to the Hanjiang River Water Transfer Project can improve the satisfaction degree of ecological water requirement of channel of the middle and lower Hanjiang River evidently.