Water environmental carrying capacity is a key factor for regional economic development and ecological environment protection. In order to ascertain accurately the water carrying capacity status of Zhangye City, this paper constructed an evaluation index system, it based on the main function positioning of each district and county, selected reasonable indexes from the four dimensions of water resources, discharge intensity, water environment and water ecology. Using analytic hierarchy process and comprehensive index method, the water carrying capacity of each district and county were evaluated, the results showed that the assessment index ranged from 63.9 to 79.4 in 2018, Minle county and Gaotai county are critical overloads, the other counties are not overloading; the assessment index ranged from 63.2 to 86.9 in 2019, Linze county and Minle county and Gaotai county are critical overloads, the other counties are not overloading; the assessment index ranged from 70.6 to 88.6 in 2020, all districts and counties are not overloading, which indicates that the water environment carrying capacity of Zhangye City is in good condition in general and has increased year by year. However, Linze County, Shandan County, Minle county and Gaotai County have just broken away from "critical overload", and the advantage of "no overload" state does not exist, and there is still much room for improvement.The ranking of the impact degree of the four indicators on water environment carrying capacity was different, considering the information of main impact indicators or pressure indicators provided by the evaluation results, this paper targeted measures to improve and enhance the water environment carrying capacity of different functional areas are put forward.