Abstract: Hongqi Lake is a macrophyte-type lake on the Song-Nen Plain.It has become themost important water supply source and fishery base in the Daqing Area since the waterof Nenjiang River was diverted into the lake in 1972.The vegetation coverage is about50%of the whole area of the lake.The structure and distribution of the monodominantcommunities of Phragmites communis,Typha angustifolia and Echinochloa crysgalli were analysed and the quantitative features of the mixed communities were described.Mostof the water bodies in the Daqing Area were polluted to various degrees with the openingup of the Daqing Oil-field.Due to the abundent aquatic vegetation in the lake whichcan eliminate the waste oil,absorb the heavy metals and settle the suspended substances,the Hongqi Lake has the best water quality and provides the highest fish harvests amongthe water bodies in the Daqing Area.