As a fuzzy evaluation method, the similarity method has been widely applied in evaluation on pollution level of heavy metals in soil and water environment. Due to lack of quantitative approach to point selection after optimization, this study improved the similarity method by integrating the method of the distance to the center of gravity in order to enhance the accuracy and rationality of results. The improved similarity method was applied to optimize 7 monitoring sections of the main stream of the Hun River. Then, the results were validated by Ttest and Ftest after optimization. The number of the water monitoring sections was reduced to 5 after optimization, and the water quality after optimization had no significant difference compared to that before optimization, which indicated that the improved similarity method has the advantage practical application the optimization of monitoring sections of water quality.