The western region of the Qinghai-Tibet Plateau is characterized by an arid climate with minimal rainfall, making groundwater the primary water source for local towns. In recent years, levated concentrations of arsenic(As), fluoride(F-) and nitrate(NO3-) in groundwater have raised concerns about drinking water safety. This study, collected 52 groundwater samples from wells in seven towns across six basins in the Ali region. By employing methods such as mathematical statistics, major ion ratio analysis, the Entropy-Weighted Water Quality Index (EWQI), and Monte Carlo simulation, the characteristics of hydrogeochemical components, controlling factors, and potential risks of groundwater in this region were clarified. The groundwater chemistry type is dominated by HCO3-Ca, and its ion concentration from high to low is Ca2+ > Na+ > Mg2+ > K+ and HCO3- > SO42- > Cl- > NO3- >F-. The most severe As pollution (0-0.09 mg/L) occurred in Gaer(GR)and Geji(GJ) towns within the Shiquan River Basin in the western part of the study area, This is primarily attributed to high As hot spring discharge, ion exchange, and the weathering and dissolution of As-containing minerals in silicate rocks Elevated F- concentrations (0.01-1.41 mg/L) were observed in Gaize(GZ) of the Luoren River Basin and Ritu(RT) of the Maka River Basin, driven by evaporation and the dissolution of F--containing minerals in evaporitic salt rocks and silicate rocks. NO3- concentrations ranged from 1.44-30.2 mg/L, and were mainly influenced by human activities. Groundwater quality was evaluated using the EWQI method. Groundwater samples from Gaer(GR)and Geji(GJ) in the Shiquan River Basin exhibited poor to very poor quality, while samples from the other five towns ranged from excellent to good. Health risks were simulated using the Monte Carlo method, revealing that both carcinogenic and non-carcinogenic risks require attention, particularly in the Shiquan River Basin, where As pollution is significant. The effective exposure factor (EF) was the most critical parameter influencing health risks, followed by As concentration and body weight (BW), with BW showing a negative correlation and other parameters showing positive correlations with risk. This study offers new insights into groundwater pollution control mechanisms and associated health risks in the western urban area of the Qinghai-Tibet Plateau. It also provides valuable references for groundwater resource management and pollution prevention in the region and downstream South Asian countries.