Abstract: In order to reduce the uncertainty of the environmental assessment,this paper constructeda fuzzy groundwater evaluation model on the basis of the trapezoidal fuzzy theory and the monitoring data from 2017 to 2019. Through field investigation the authors revised the exposure parameters for the research of Yimuquan groundwater.The results show that the total health risk of the water source is between 2.959×10^-5~1.504×10^-4a^-1,not exceeding the generally accepted Ⅲ risk level with the credibility of over 55%.However,in the upstream monitoring point,the risk has exceeded the Ⅲ level that should be given more concern.The primary risk substance is Cr because of the richness of Crin the original environment and the long-term exploitation of groundwater.In terms of different receptors,females have a higher risk than males,and adults higher than children.Compared with the traditional model,trapezoidal fuzzy evaluation model can better describe the risk of critical state and is more applicable than the triangular fuzzy model.Trapezoidal fuzzy model and appropriate exposure parametersare important to reduce the uncertainty,though the uncertainty of the model needs further study.