Duolun County, located in the Xilingol League, is a typical agro-pastoral ecotone in the north and is also the source of the Luan River system. Whether the development and utilization of regional water resources are reasonable and whether the water ecological environment is sustainable are the key issues that local government departments cannot ignore. By investigating the current situation of water resource development and utilization in Duolun County, this study revealed that the per capita water usage and the water usage per ten thousand yuan of GDP in Duolun County in 2020 were lower than the average level in the Inner Mongolia, and the level of water usage was relatively better. By using the nine-scale method and the analytic hierarchy process to construct an evaluation model of the water ecological environment of Duolun County, the comprehensive score of Duolun County was 8.35 (total score is 10), indicating that the water ecological environment in the study area was currently in a good state. The evaluation model has reference value for the future management of the water ecological environment in Duolun County and for continuous related research.