Abstract:To objectively and effectively evaluate the service value of a river ecosystem and to efficiently develop and utilize river resources, firstly, the ecological service effect of instream flow is revealed based on its characteristics and functions. Then, according to its compositions, characteristics, utility and functions, the concept and classification of service functions(values)of the river ecosystem are discussed. Finally, taking the instream flow as the quantitative index, an evaluation model for the service value of the river ecosystem is established, and the evaluation method for its service value is introduced. The research results reveal the complex function relation between the service value of river ecosystem and the instream flow in terms of service effects and evaluation model, and this study may provide a new idea for river management departments to efficiently develop and utilize and to scientifically plan and manage water resources of rivers.