This article reported the start-up process of sludge digestion supernatants treatments by CANON process based on MBBR reactor. The pilot system with a volume of 8.55m³ was used and filled with SPR-Ⅲ filler, which had a filling rate of 44%. The CANON process was successfully started after 70d with dynamic inflow of CANON sludge, and the inoculation ratio was below 1%. After 200d, the TN removal volumetric loading was stable at 0.9kgN/(m³·d), the mean value of the concentration of effluent ammonia nitrogen was 63.9mg/L, and the removal rate of ammonia nitrogen and total nitrogen were 91% and 85% respectively. The N-removal pathway ofdenitrificationand anaerobic ammonium oxidation occurred simultaneously due to small amount of organic matter presence in the influent, which accounted for 5% to 7%and 93% to 95% of total nitrogen removal, respectively. By controlling of pH and aeration intensity, the scaling of suspended carriers was prevented and the relationship among DO, aeration intensity and biofilm thickness was balanced. As a result, the biofilm always maintained suitable thickness, which stabilized the treatment effect of the system. The high flux sequencing indicated that AOB and AnAOB were dominant species on the suspended carriers, and their abundance reached 17% and 14% during steady operation. There was no NOB in the system, indicating that the short-nitrification effect was good. The denitrifying bacteria abundance was 2%~3% and relatively stable, indicating that the small amount of organic matter in the influent did not affect the increase of anammox bacteria.