Aimed at the severe ecological problems such as large scale development of water resources, over-exploiting groundwater and cutting off of plain rivers in the Xiliao river basin, the paper considered the ecological flow and groundwater level of river as a whole, and systematically determined the composite ecological water requirement.First, it calculated the minimum river flow and appropriate ecological flow;secondly, taking bank of river as objective and ecological flow as confine condition,according to the relation between replenishment and discharge and avoiding salinization, the paper determined the ecological groundwater level that can support the ecological flow of rivers. The composite indexex of ecological water requirement are composed of minimum river flow, appropriate ecological flow and ecological level of groundwater,which can provide scientific reference for the plan and management of water resources, protection and recovery of water ecosystem in that region.