Comprehensive assessment of eco-environmental water requirement in arid inland river basins is a multilayer and multi-objective subject for decision-making.At the same time,it is one of key scientific problems to be solved in the reasonable allocation and management of water resources and eco-environmental protection and construction in arid regions.According to the real conditions and environmental problems confronted in the Tailan river basin,an indicator system composed of three hierarchies with 38factors was established to assess the eco-environmental water requirement.The indicators were quantified by classification, and the weights of all factors were calculated by the method of analytic hierarchy process(AHP).Criterion and specific methods were proposed to judge the status of eco-environmental water requirement in the basin. The assessment results indicate that for eco-environmental water requirement,the water resource factor was the dominant ones,the natural factors were the least ones;and the economic-social and eco-environmental factors were the intermediate ones.These four types of factors interrelated with each other,which in combination determine the eco-environmental water requirement.The assessment results agreed well with the reality, which suggests this method is of application value