The purpose of this experiment is to explore the effect of an anaerobic/anoxic/aerobic process test device on the treatment of simulated aquaculture tailwater. In the enrichment stage of denitrifying phosphorus accumulating bacteria, after three stages of an enrichment culture of activation of phosphorus accumulating bacteria, enrichment of denitrifying phosphorus accumulating bacteria, and keeping the system stable, the phosphorus removal rate of the system reaches 80%. During the treatment of simulated aquaculture tail water with denitrifying phosphorus removal bacteria, the A2/O process experimental device continuously influent and effluent, and the removal rate of nitrate nitrogen in the effluent of the system reached 95% in the whole process. The removal rate of phosphate in the effluent is 40%~50%, the removal rate of total nitrogen in the effluent is also stable at 88%, and the removal rate of total phosphorus in the effluent is 30%~50%. When exploring the treatment effect of the A2/O process test device on the treatment of high nitrate biological floc tail water and circulating aquaculture tail water, the carbon source was added to maintain the carbon-nitrogen ratio of 3.4:1 by adding sodium acetate as a carbon source. The denitrification effect of the group is remarkable, the phosphorus removal effect is not significant, and it does not meet the first-class discharge standard of SC/T9101-2007 "Freshwater Pond Aquaculture Water Discharge Requirements" and needs further treatment.