This paper discussed the advance in ecological and environmental water requirement (EEWR) study, including its conception, classification, calculation methods, and others. At abroad, the EEWR study is concentrated on rivers, and a more applicable methodology has been established; while in China, it is focused on land and river in the interior river basins of the northwestern areas, the Yellow River Basin, the Haihe river basin and the Luanhe river basin, where the water shortage problem is serious. Many achievements of great significance in the EEWR study at home and abroad have been achieved, but there are still many other ambiguous and unknown issues to be further studied in the future, summarized as: (1) the studies on the EEWR theory (including its conception, classification, calculation methods, etc.) should be strengthened; (2) it is necessary to reinforce some aspects of the EEWR study, such as the internal and external affecting factors of EEWR, the engineering approaches or measures to meet EEWR, etc.; (3) it is urgent to expand the applied research of EEWR and to realize the optimized allocation of water resources.