[Objective] The water quality of cold alpine wetland in Gansu Yanchiwan National Nature Reserve was investigated and evaluated to understand the security status of water resources in this area, and to provide basis for drinking water security and downstream safety water supply.[Methods] Twenty-six water samples were collected in the Gansu Yanchiwan National Nature Reserve, including 17 riverine wetland water samples, 3 lake wetland water samples, 5 marsh wetland water samples, and a thermal spring water sample. The pH value, total hardness, nitrogen content, permanganate index, anionic surfactant, chloride content, total phosphorus content, and the contents of the metal ions, Zn, Fe, Cu, Cd, Cr and Pb, were measured according to the national standard. The determination results were evaluated by single index evaluation method, comprehensive index evaluation method and Nemerow index method.[Results] ① All the water samples were alkalescent. ② The hardness of sampled water were all moderate. ③ The water of Xiaoquan marsh wetland was polluted by nitrogen; fifteen water samples were polluted by anionic surfactant; Xiaoderji Lake, midstream of Dahe River and midstream of Dashuihe River were polluted by Cd; midstream of Dashuihe River was also polluted by Pb; and eleven samples were polluted by Fe.[Conclusion] Most wetland water quality were good, reached to I or Ⅱ level of national surface water standards. The water quality of midstream of Dahe River, midstream of Dashuihe River and Xiaoderji Lake were all worse. Nemerow index method was identified as the optimum method for the evaluation on water quality of National Nature Reserve.