Abstract: The effect of purifying eutrophic marine water by tropical and subtropical bivalve shellfish Paphia exarata Philippi and tropical macroalgae Kappaphycus striatum Schmitz was examined. The results show that the polyculture of Paphia exarata Philippi and Kappaphycus striatum Schmitz is a effective way to remove the N, P, and chla in eutrophic water. The effect of Kappaphycus striatum Schmitz on the comprehensive evaluation index, clearance of N, P and chla is more notable than Paphia exarata Philippi. Kappaphycus striatum Schmitz significantly affected all the indicators (P <0.01). Paphia exarata Philippi significantly affected the clearance of N and chla (P <0.01), but it was not significant effecting on the comprehensive evaluation index and the clearance of P. The best polyculture proportion wes obtained, which correspond to Kappaphycus striatum Schmitz of 6 Kg/m3 and Paphia exarata Philippi of 60 bodies/m3 (40g±2g/body).