Aiming at the problem of the relative static state of the standard fuzzy comprehensive evaluation method and the simplification of the membership function, the dynamic variable fuzzy comprehensive evaluation method is used to establish the evaluation index system of groundwater quality first, and the objective weight of the evaluation index is determined by the entropy method. The analytic hierarchy process determines the subjective weight, and combines the subjective and objective weights to determine the dynamic comprehensive weight of the evaluation index. And then constructs the variation range of groundwater quality assessment.Considering the groundwater hydrogeology, spatial distribution characteristics and the actual situation of aquifer, the membership function of water quality evaluation in the past fuzzy comprehensive evaluation method is extended from linear function to non-linear function, which is more suitable for groundwater quality evaluation. This model is applied to the evaluation of groundwater quality in Guyuan City and the results show that the water quality levels of the monitoring wells 1 and 2 are grade Ⅳ and the monitoring wells 3, 4, 5, 6 and 7 are of grade Ⅲ, which is in accordance with the actual situation of groundwater in this area after analysis. The dynamic variable fuzzy comprehensive evaluation method is used to evaluate the groundwater quality. The results are objective and reasonable, and have good practicability.