Abstract: At present groundwater quality assessment method is numerous, and the selection of the appropriate assessment method is of great significance to the management and utilization of groundwater. Based on the detection results of groundwater samples collected in Chaoyang District, Beijing during the dry season in 2020, the improved analytic hierarchy process (AHP), single factor index method and comprehensive pollution index method were used to assess the groundwater quality, and the accuracy and irrationality of the assessment results of different water quality methods were compared. The results showed that: 1) The results of different water quality assessment methods varied greatly, the improved AHP was the best, the single factor index method was the worst, and the comprehensive pollution index method had the highest consistency with other methods. 2) In water quality assessment, the comprehensive pollution index method could be preferred. The single factor index method was suitable for water with high water quality requirements or few pollutants exceeding the standard. The improved AHP was suitable for water with multiple pollutants exceeding the standard. 3) In order to further determine the accuracy of groundwater assessment by different methods, the reliability analysis of different water quality assessment methods was carried out. The improved AHP, single factor index method and comprehensive pollution index method accounted for 90.48%, 42.86% and 47.62%, respectively, of the water quality assessment results that were the same as those in the reliability analysis. Therefore, in the comprehensive assessment of groundwater quality, the improved AHP could be used.