The invention discloses a method for utilizing myriophyllum elatinoides for treating tail water of a sewage plant. The method comprises the steps that the tail water of the sewage plant is conveyed to a tail water receiving area, the water depth in the tail water receiving area is 0.2-1.0 m, and water power staying time of the tail water in the tail water receiving area is controlled to be 2-10 days; myriophyllum elatinoides accounting for 20-60% of the water body area are planted in the tail water; the myriophyllum elatinoides planted in the tail water receiving area are harvested every 20-30 days. According to the method for utilizing the myriophyllum elatinoides for treating the tail water of the sewage plant, a nitrogen and phosphorus removal mode of rhizospheric microorganism purification, aquatic plate uptake and the like can be formed, and the quality of output water of tail water nitrogen and phosphorus stably reaches over an earth surface IV-class standard. A brand-new path for purifying the tail water deeply is provided, and the method has good economic benefits and social benefits.