This research attempted to make a systematic summary as well as commentary towards the previous studies concerning ecological water requirements in the mainstream and estuarine ecosystem of the Yellow River Basin (YRB). The status and challenges of ecological water requirements in the mainstream and estuary of the Yellow River have been summarized in terms of research objects, contents, research methods and applications of ecological water requirements studies. At present, the research on the ecological water requirements of the mainstream and the estuary of the Yellow River has achieved certain results. The basic laws of the theory of ecological water requirements in the Yellow River Basin were relatively clear. The water calculation methods are not uniform. There are certain errors in the calculation results, which makes it difficult to achieve the expected results in the practice of water resources allocation and management in the YRB. In the future, the focus on the researches of Yellow River ecological water requirements should be based on the ecological water requirements of rivers and wetland ecosystems; researches on eco-hydrological process of ecosystem based on eco-hydrological model; finding the reasonable ecological water requirements considering the economic, social, environmental win-win trade-off and other uncertain factors, that can be applied to the actual water allocation scheme. Moreover, on this basis, the results of ecological water requirement and the ecological regulation of the Yellow River water volume can be combined and demonstrated in the ecological water regulation of the Yellow River in practice.