Based on an analysis of impacts of hydropower development on the ecological environment, research progress in ecological protection measures during hydropower station construction and operation is summarized, including construction of fish passage facilities, establishment of fish proliferation and release stations, methods for determination of ecological flow downstream of dams, and ecological operation of cascade reservoirs, and the disadvantages of the ecological protection measures in cascade hydropower development are illustrated. Accordingly, the ideas of cooperative determination of the water head in river cascade hydropower development and the ecological water head are discussed. Furthermore, the concept, implications, and principle for definition of the ecological water head are presented based on natural river habitats, natural ecosystems, and species protection, and a comprehensive optimization method is proposed for ecological water head planning.