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The embedding immobilization technology can provide a carrier for microorganisms to improve the ability of microorganisms to remove nitrogen-containing pollutants in the biological aerated filter (BAF) of the recirculating aquaculture system. Based on polyvinyl alcohol-sodium alginate (PVA-SA) composite carrier material, 0%~2% (w/w) cyclodextrin (β-CD), diatomite (DIA) and zeolite (Z-13X) were added. The mechanical strength, physical and chemical stability, reusability, nitrification performance and internal structure of the composite carrier were investigated by orthogonal experiment, physical and chemical properties, water quality monitoring and scanning electron microscope analysis. The results showed that the optimum composite ratio of composite carrier was PVA 10%, SA 2%, β-CD 0%, DIA 2% and Z 1%. The composite carrier with this ratio had good mechanical properties. The modified composite carrier could be applied to acidic tail water, and its internal structure was porous, and the pore size was suitable for microbial growth. At the same time, an efficient nitrifying strain Halomonas sp. NH2B was screened and embedded in a composite carrier for further research. The microbial composite carrier could remove 100% NH4+-N at an initial concentration of 50 mg/L after 36 hours, and after seven cycles, the pore structure of the composite carrier remained basically unchanged, and there were microorganisms attached. The NH4+- N removal rate could still reach 76.93%. In summary, the new composite carrier material can effectively solve the problems of weak viability and strain loss after microbial inoculation, ensure the nitrification efficiency and improve the reusability. [ABSTRACT FROM AUTHOR]