A 0.19 hectare natural-type wetland for stream water treatment demonstration was constructed and planted with cattails from April 2001 to May 2001. Part of its bottom surfaces adjacent to levees have a variety of slope of 1 : 4~1 : 15. Two small open water areas were installed, in which emergent plants could not grow. Removal of nutrients from stream waters was a major objective of the wetland. Waters of Sinyang Stream flowing into Kohung Estuarine Lake were pumped and funneled into the wetland. The lake had been formed by a salt marsh reclamation project and was located southern coastal region of Korean Peninsula. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow and outflow averaged $120.4m^3/day$ and $112.1m^3/day$, respectively. Hydraulic retention time was about 3.1 days. Average total phosphorous concentration of influent and effluent was $0.19mg/{ell}$ and $0.075mg/{ell}$, respectively. Total phosphorous loading rate of inflow and outflow averaged $12.05mg;m^{-2};day^{-1}$ and $4.44mg;m^{-2};day^{-1}$, respectively. Average total phosphorous removal rate in the wetland was $7.61mg;m^{-2};day^{-1}$. Seasonal changes of phosphorous retention rates were observed. The wetland acted as effective phosphorous sinks in the initial stage of the constructed wetland.