Boron (B) resources in Dangxiong Co (DC) salt lake of Tibet, China. It is a largesized borate deposit. Atmospheric deposition, surface runoff, groundwater and rocks in erosion source area are sources of trace and dispersed elements (including B) in DC salt lake in Tibet. Geochemical characteristics of these sources were studied using GB/T85382008, ICPAES, and ICPMS in this paper. Results show that, ①The annual input of B2O3 from atmospheric deposition to the DC salt lake is 005×10-3~15×10-3 t, which is negligible compared to 893 t from surface runoff and groundwater inputs. ②Rivers are the most contributors of B2O3 to DC salt lake. The three rivers on the south bank of the DC salt lake contribute 95% of B2O3. The geochemical characteristics of the water of these three rivers are the same to the Maerzuo hot spring. In addition, the δ11B value is also same to that of Maerzuo hot spring. These results indicate that B2O3 in surface runoff and groundwater is from hot spring. ③The rocks in erosion source area are mainly Permian and Cretaceous strata rocks and Carbonate clay and travertine of Quaternary strata. The B2O3 concentrations of of Permian and Cretaceous strata around DC salt lake are lower than that in similar rocks in eastern China, that indicate the Permian and Cretaceous strata in DC are not the main source of Boron in DC salt lake. Carbonate clay and travertine of Quaternary strata around DC salt lake have a high content of B2O3, higher than carbonate rocks in the world and eastern China. The rare earth elements (REE) distribution patterns of carbonate clay are same as that of reported thermal water lacustrine deposit dolomite, characterized by middle REE enrichment and Dy positive anomaly. This indicates that carbonate clay around DC salt lake is lacustrine deposit affected by hot spring. The carbonate clay in DC is a typical example of lacustrine hydrothermal deposits. All these results above prove that thermal water is the main source for boron in DC salt lake. This study not only provides important theoretical references of the origin of B in Salt Lake, but also has significantly importance to further exploration of borate deposits in China.