Shishahai Lake is a scenic and sightseeing lake in central Beijing.Before the ecologic recovery testing, it was under heavy eutrophication.Indexes of B0D₅;NH₃-N, Permanganate Index and TP were over Y-Class of Chinese Environmental Quality Standards For Surface Water with dominant alga of bellamya microcystis.Several technologies were used in the ecological recovery for Lake Shishahai, i.e., ozone/supersonic algae removal, aeration, floating bio-bed technology, lake bottom recovery, hydrophyte planting and recovering and biological adjustment and control.After more than ten months' testing of ecological recovery, the ecological environment has improved obviously.TN and TP content are 1.26mg/L and 0.046mg/L, which were reduced 79% and 91% separately for TN and TP.Meanwhile, the chlorophyll.a content was decreased with notable deeper transparency in the lake.The general evaluation of water quality is IY Class.