In view of the present main environmental problems in the Tailan River basin, based on the types of eco-environmental water requirement for river basins,quantification model of eco-environmental water requirement for plain regions of Tailan River basin is established and the scale of eco-environmental water requirement is estimated.The results indicate that the maximum of eco-environmental water requirement is 4.146×10⁸m³,the minimum is 2.372×10⁸m³ and the optimum is 2.983×10⁸m³,which take 51.05%,29.21% and 36. 73% of the regional watergross,respectively.Average eco- environmental water requirement in Tailan River is 1.440×10⁸m³when excluding water requirement of sand transportation,and 2.604×10⁸m³if considering the water requirement of sand transportation.According to environmental status and the aim of ecological protection,eco-environmental water requirement in river basin can be ascertained.Consequently,water resources use will be allocated in different area and different usage department,and the rational scheme of water resources in ecology will be confirmed based on the different status of eco system and corresponding types of ecosystem in arid in land river basin.