Abstract: Based on the analysis and comparison of domestic and foreign research methods, with discussion of application principle, data verification and background values, the mathematical statistics are adopted to study the environmental background values of quality indexes such as TDS, Ca²⁺, Mg²⁺ and Na⁺ of the groundwater in Middle Yarlung Zangbo River Basin of Tibet, as well as the spatial distribution and controlling factors of the indexes. The results show that spatial distribution is mainly affected by topography and regional hydrodynamic conditions, which provides scientific references for the evaluation on groundwater pollution status in the study area.