Abstract: The effects of the rehabilitation of submerged vegetation on water quality improvement were investigated by using large scale enclosure system which were installed in a hyper eutrophicated lake,Lake Donghu in Wuhan.The results shown that the transparencies in the enclosures with macrophytes were considerably enhanced compared with the control enclosure without macrophytes and the lake water,while the apparent water color was decreased.COD Cr and BOD₅ were about 20 and 5 mg/Lrespectively in the macrophyte enclosures,while those of the control enclosure and lake water were at the level of 40 and 10 mg/L.The number of detected organic pollutants isolated from the water body of macrophyte enclosures was also lower than that of the control enclosure and the lake water.It was demonstrated that the water quality could be significantly improved by reconstructing aquatic macrophytes.