Gehu Lake, situated in Jiangsu Province, is a shallow one with an area of 164 km².It is rich in submerged pliints, of which about 80% is covered by polamogeton maackianus, In order to improve aquatic macrophyte communities, it is necessary to control and even weed out the growing and spreading relative water plant.This work was carried out in 1988-1990.According, to the results of weeding,by herbicide and by herbivrous fishes, it is concluded that biological control of aquatic macrophytes in pen fishculture and in pen fishgrazing has played an obvious significance in improving the aquatic macrophyte communities in the weedy lake.