Abstract:The variation of uranium and its isotopes in water environment is of great significance for the protection of regional ecological environment. At present, there are few reports on the study of uranium and its isotopes in the water body of Lhasa River, which is in an environmentally sensitive area. In order to understand the distribution characteristics of uranium and its isotopes in the water body of Lhasa River Basin, the contents of uranium and its isotopes (238U, 235U and 234U) in the water samples collected from 16 sampling points in the middle and lower reaches and Duilonqu tributary of Lhasa River in July 2017 were measured and analyzed by inductively coupled plasma mass spectrometry (ICP-MS) element 2. The results show that the uranium concentration in the water body of Lhasa River is significantly higher than the average uranium concentration in the World Rivers, equivalent to that in the river water of Qinghai Tibet Plateau and slightly lower than that in the main stream of the Yellow River. Uranium and its isotopes have homology with K+, heterologous with Mg2+ and SO42-, but have no significant correlation with other hydro-chemical parameters. 235U and 238U in Lhasa River have good correlation, and there is no significant isotopic fractionation. The high (234U/238U)AR value in the Lhasa River is mainly due to the enrichment or loss of 234U in the water body. Under the influence of water rock exchange, 234U is easy to enter the water body under the action of α ecoil. The sampling points near Yangbajing have the characteristics of high uranium concentration, which reflects that its water environment has good oxidation conditions.