Abstract: In order to optimize the functionality of the Middle Route Project of South-to-North Water Diversion and minimize the adverse environmental impacts arising from operation of the project, the major ecological and environmental problems and the risks in the water source area, the main canal, and the middle and lower reaches of the Hanjiang River due to operation of the project were analyzed and discussed. The main environmental problems in the Danjiangkou Reservoir, the water source, include agricultural non-point source pollution, heavy metal pollution and ecological fragility in the reservoir fluctuated zone. The main environmental problems in the main canal include algae and shellfish proliferation and the risk of pollution due to traffic accidents happening on the bridges crossing the canal. In addition, there were potential risks of water pollution caused by surface water overflow, groundwater infiltration and settlement of atmospheric pollutants. The ecological and environmental problems caused by the water diversion were the eutrophication and algae blooms in the middle and lower reaches of the Hanjiang river due to decrease of upstream flow. Some suggestions have been made to address these problems and mitigate the risks.