Abstract: By adding the composite functional bacterial agent Eure-01 in the O-section of the traditional A/O process, the treatment of tannery wastewater was realized in terms of segmental enhanced decarburization and denitrification. The succession of functional flora and the corresponding changes of metabolic function of each biological treatment unit were explored after the enhancement of bacterial agent. The effects of different activation methods of inoculants on the decarbonization and denitrification efficiency were investigated; metagenome analysis and carbon metabolism fingerprints based on Biolog plates were used to analyze the different inactivation methods on the microbial community structure in the microbial agent and activated sludge system during the strengthening process. Results showed that after the addition of the multi-stage activated fortifier, the removal rates of COD and NH₃-N in the aerobic tank were increased by nearly 50% and 40%, respectively, compared with those without the intensifier. After the multi-stage intensive activation of the bacterial agent, the carbon source of the bacterial flora exhibited good metabolic activity, balanced functions and improved utilization of the carbon source. Furthermore, the carbon source metabolic activity of the bacteria group was balanced and the higher species diversity level was observed. Microorganisms of Xanthomonadaceae and Burkholderiaceae with the ability to enhance ammonia nitrogen in wastewater could account for 25.7% and 22.3%, respectively. The present inoculum-enhanced A/O process has obvious effect on large-scale tannery wastewater treatment, and provides a set of highly efficient decarbonization and denitrification staged biological intensive treatment technology and microbial ecological interpretation for tannery wastewater treatment.