Abstract: According to the features of the natural conditions and water resources utilization of the Changjian River, the definition of environmental flow, calculation principles and method were discussed. With several examples, such as Hutiaoxia in Jinsha River, Jinping in Yalong River, upper Ming River and the estuary of Changjiang River, the problem how to make a decision about environmental flow in Changjiang River Basin was analyzed. On the basis of our research on wetland area, like Changjiang River, environmental flow should be considered from the whole basin. Before ecological problems have not been fully clarified, the environmental flow should be maintained a larger flow.