Abstract: Analysis of the causes of water environment problems is the key way to support the water environment fine-management and water eco-environment recovery in the river basins. The Air-ground-water integrated model system was applied to establish the response model of water quality to pollution sources in Xiangxi River Basin, and the water environment problems in the basin were quantitatively analyzed. The model was verified according to the measured data of the water quality monitoring sections in 2019, and the relative error of total nitrogen (TN) and total phosphorus (TP) concentrations were within 10%. The results showed that sewage treatment plants, industrial enterprises and livestock breeding were three main sources of water pollution and eutrophication of Xiangxi River Basin, with a total contribution rate of more than 60%. For Sixiangxi section, TN and TP discharge from sewage treatment plants were 193.28 and 40.51 t/a, with 226.25 and 31.69 t/a from industrial sources, and 187.75 and 29.82 t/a from livestock breeding, respectively. For Changshaba section, TN and TP produced by sewage treatment plants were 376.31 and 48.97 t/a, with 295.30 and 39.91 t/a from industrial sources, 128.09 and 41.61 t/a from livestock breeding, respectively. Based on the urgent needs of comprehensive water environment management, the efforts to control pollution of these three kinds of sources should be intensified in the future.