[Objective] The chemical characteristics of groundwater in Beichuan River basin were analysed, and groundwater quality was evaluated objectively from the perspective of resource attributes of groundwater in order to provide data support for regional groundwater environmental protection. [Methods] 189 sets of groundwater chemical data acquired by hydrogeological surveys in 2019 were selected to analyze the distribution characteristics and sources of groundwater chemical composition in Beichuan River basin. An evaluation method for regional groundwater quality was constructed by assigning different coefficients for water quality type to a single sampling point. [Results] The groundwater chemical distribution of Beichuan River basin exhibited a large spatial variability. HCO₃-type freshwater was widely disturbed in the upstream sections of the hilly mountainous area and the valley plain area , and SO₄^2-, Cl-type brackish and salt water, as well as HCO₃·Cl-Na type freshwater gradually appeared downstream, indicating human activities. Weathered dissolution of carbonate rock and silicate rock controlled the source of groundwater chemical components, but local areas were enriched due to evaporation concentration. Natural background elements such as Al, Fe, and Th were the main influencing indicators that had exceeded the underground water quality standard in the study area, but typical contamination components such as Pb, NO₃^-, and carbon tetrachloride were more obvious in the industrial zone and the population-concentrated area. Under the driving influences of human pollution and naturally high background conditions, the underground water quality in the river valley plain was more complicated. The over-standard ratios of the hilly mountainous region and the valley plain region based on the quantity of sampling points were 57.0% and 27.1% respectively, but these values were reduced to 29.4% and 12.6% according to the new evaluation method proposed in this study. [Conclusion] The impact of human pollution on the chemical components of groundwater was mainly concentrated in middle and lower reaches of the valley plain zone, and chemical components of groundwater in most other regions were controlled by natural background conditions. Through the newly proposed regional groundwater quality evaluation method, groundwater quality evaluation results and groundwater resources were combined, and the proportion of abundant high quality groundwater area was highlighted in the whole area. Finally, the problem of excessive over-standard rate in the regional groundwater quality evaluation results was effectively resolved.