Abstract: In this paper, the feasibility of advanced treatment in tannery secondary effluent by O₃/H₂O₂-MBBR (Moving Bed Biofilm Reactor, MBBR)-O₃/H₂O₂/UV combination process was studied. The effects of O₃ and O₃/H₂O₂ pre-oxidation on the biodegradability, nitrogen conversion and removal were investigated. Meanwhile, the catalytic ozonation was combined with MBBR, and the removal efficiency of COD_Cr, ammonia nitrogen and total nitrogen was evaluated. The results showed that O₃/H₂O₂ pre-oxidation can significantly improve the biodegradability of tannery secondary effluent compared with O₃ pre-oxidation. The ratio of B/C (BOD₅/COD_Cr) increased from 0.016 to 0.18 after O₃/H₂O₂ pre-oxidation. Moreover, the O₃/H₂O₂ pre-oxidation can transform organic nitrogen into inorganic nitrogen, and enhanced nitrogen removal in biochemical process. Through the pilot test of O₃/H₂O₂-MBBR-O₃/H₂O₂/UV combined process, the average COD_Cr, ammonia nitrogen and total nitrogen of the effluent were 38.69 mg/L, 1.19 mg/L and 11.35 mg/L, respectively. The removal rates were 83.31%, 91.00% and 57.00% respectively.