Abstract: The F_i of Nemero index method mutates at all levels close to the threshold value of water quality. The calculated F does not match with the classification of groundwater quality standard, and F_max has excessive influence on F. In order to solve these problems, a new improvement of Nemero index method has been proposed. On the premise of not changing the expected value of F_i, this method makes F_i continuous, and appropriately increases the influence of F on F. This method is applied to the comprehensive evaluation of groundwater in the study area. The results show that after improvement, F becomes more continuous and uniform, and the balance of the influence of F and F_max on F has been improved. The improved F reflects the status of groundwater quality more objectively.