In order to solve the contradiction between ecological maintenance and agricultural production water demand, the minimum water demand for ecological restoration in arid areas was determined. The lower reaches of the Tarim River were selected as the typical study area. Suitable areas for vegetation growth were determined through the PNV (potential natural vegetation) simulation method, while the suitable growth ranges and distribution areas of trees, shrubs, and grasslands were analyzed. The minimum ecological water demand for the lower reaches of the Tarim River was calculated by the multi-year evapotranspiration data from the AET dataset. The results show as follows. The PNV results obtaine in the lower reaches of the Tarim River are dominated by shrubs, forests and grasslands are highly dependent on water resources, mainly distributed around river channels. The forest and grassland in the study area show high growth potential, while the shrub distribution areas far from the river show a degradation trend. According to PNV simulation results, the ecological water demand in the lower reaches of Tarim River is about 11 279.23×10⁴ m³, of which shrubs account for the largest proportion, while woodland and grassland account for 7.4% and 5.36% respectively due to their small areas. The research results provide a new method for ecological restoration and determination of water transport capacity in arid areas, which can clarify the scope of ecological restoration and vegetation types in the basin, and contribute to the management and optimal allocation of regional water resources.