For solving the problems occurred in the process of surface water utilization,the the-ories of ecological and environmental water requirements of river course are studied in this pa-per.The following conclusions are mainly drawn:(1)Based on the analyses of the old concept s of ecological and environmental water requirements,definitions of ecological water requirement and environmental requirement are given.(2)The ecological water requirements and environ-mental water requirement of river course are expounded especially theoretically.Firstly,the con-cepts related to the research of ecological and environmental water requirements of river course have been reviewed.Secondly,the mechanism and composition of ecological and environmental water requirements of river course are discussed according to the balance of river water quantity.Thirdly,according to the impacting intensity of human being on surface water,the exploitation and utilization of water resources are divided into four stages,and the characteristic of river e-cosystem of each stage is described.The impacts of river flow reduction on the whole river e-cosystem are analyzed.Finally,the concepts of ecological water requirement and environmental water requirement of river course are given on the basis of the above analyses.The research of this article can provide some theoretical foundation and basis for the study of ecological and en-vironmental water requirements of river course.