The　aim　of　this　study　is　to　investigate　the　oxygen　mass-transfer　characteristics　of　a　turbine　surface　aerator　with　vertical　shaft.　Full-scale　test　tank　platform　were　used　for　this　purpose.　As　a　result,　a　model　was　set　up　with　the　aid　of　Matlab.　It　has　been　found　that　there　are　a　maximum　power　efficiency　point,　a　sub-maximum　power　efficiency　point　and　a　minimum　power　efficiency　point　for　this　type　of　surface　aerator,　and　the　submergence　is　283.5　mm　and　the　rotational　speed　is　29.73　r/min　at　the　maximum　power　efficiency　point.　This　result　shows　that　it　should　be　controlled　at　the　maximum　power　efficiency　point　in　operation,　and　the　depth　of　immersion　should　be　kept　constant　at　the　range　of　rotational　speed　from　27.27-32.88　r/min　and　input　power　from　81.3-131.4　kW　for　this　aerator　in　some　occasion　so　as　to　get　high　power　efficiency　in　operation.　The　input　power　is　101.5　kW　at　the　maximum　power　efficiency　point,　and　the　maximum　input　power　is　131.4　kW　in　high　power　efficiency　area.