The development of water resource affects natural runoff obviously. An indicative fish can be chosen as one of bases for ecological flow establishment, which is useful for health of river ecosystem. On the basis of situation of fishy habit and resource, especially in connection with spawning，feeding and migratory environments, of rare fishes and main economic fishes in the main stream of upper Changjiang River, the indication of the fishes is quantitatively evaluated with 10 indices belonging to aspects of species value, feeding，spawning and migration. The result shows that the paddlefish may be used as an indicative fish to establish ecological discharge, because it can represent hydrological requirements of aquatic biology in the main stream of upper Changjiang River.