Abstract: Samples were collected once a month from July 30th to December 2nd from the influent and effluent waters of an aquicultural farm,dominated with fish-mussel polyculture,a mode of circular economy in pond acquiculture.Total phosphorus(TP),total nitrogen(TN),orthophosphate phosphorus(PO3-4-P),nitrate nitrogen(NO-3-N),nitrite nitrogen NO-2-N),ammonium nitrogen(NH+4-N),CODMn and chlorophyll-a(Chla) in the samples were analyzed as main quality indexes for evaluation of effect of the polyculture on purifying waste water.Results show that removal rates of all the pollutants,except for Chla,first increased and then decreased during the experiment.The removal rate of NH+4-N ranged from 25.58% to 50.82%,with an average of 38.05%,and the highest appeared on August 28th and the lowest on December 2nd.The removal rate of NO-2N,NO-3-N,PO3-4-P,TN,TP,and CODMn varied from 16.95% to 45.45%,25.23% to 48.48%,18.37% to 52.43%,19.47% to 49.39%,12.24% to 50.00%, and 31.88% to 49.63%,averaging 26.93%,34.75%,36.50%,29.66%,32.49%,and 41.21%,respectively.What is more,they all peaked on September 29th and fell to the bottom on December 2nd.The polyculture showed significant effect in removing Chla,with an average rate being 83.49%.The values of comprehensive trophic index of the effluent water was much lower than that of the influent water of the polyculture system during the test.It could be concluded that the polyculture system is highly effective in purifying wastewater of the aquaculture farm.

Key words: Hyriopsis cumingii, circular economy pattern, polyculure area, purification effect