Abstract: After the mine closed, the pollutants in the groundwater will spread far and deep as time goes on.It is particularly important to make quantitative evaluation of groundwater quality in closed mines and take corresponding treatment measures according to the evaluation and classification results.In order to evaluate the quality of groundwater of closed mines in Longyong coalfield, total hardness, total dissolved solids, sulfate and chloridion are chosen as rating items according to the groundwater quality standard.152 groups of groundwater samples from 15 closed mines in Longyong coalfield are evaluated and classified based on the Fuzzy Comprehensive Evaluation(FCE) method.The results show that the groundwater quality of those closed mines is generally poor, and mostly belongs to the Ⅳ level and the Ⅴ level.The quaternary pore water and Tongziyan group fissure water are not suitable for the source of drinking water.The water quality of lower limestone is relatively good, but it is not suitable for mining, and it should be focused on protection.Those results provide the references for restoration of the ecological environment for abandoned mines.