Abstract: Mariculture wastewater treatment effect was quantitatively measured in the "sieve bend combined with four grade biological cleansing ponds" wastewater treatment system in one indoor fish farm at Yantai city, Shandong province, China. Experiments results showed that the removal effect of suspended solids, total inorganic nitrogen and total inorganic phosphorus was obvious in this system. Dissolved oxygen, pH, conductance, temperature and salinity of the wastewater had reached the normal value of the natural seawater before discharge. The total amount of bacteria and vibrio showed a downward trend in different ponds along with the wastewater inflowing. Demersal unicellular algae in the biological cleansing ponds were rich regarding biodiversity. Farming sea cucumber in the last two wastewater treatment ponds also created significant economic benefits. It was demonstrated that this system with low construction costs and large wastewater treatment capacity was a suitable mode for land-based industrialized mariculture wastewater treatment in China.