The objective of this study is to solve the problems related to the effluent quality in RBC process : media clogging and the biomass sloughing. Three stage RBC with Autoxidation phase was operated along with the existing three stage RBC operation by varying the operational parameters in order to compare removal efficiencies of organics and nitrogen. The BOD removal efficiencies in the three stage RBC with Autoxidation phase were over 95% at a organic loading of 98.4g BOD/㎡/day. The existing three stage RBC process showed a 95% removal at a organic loading of 49.2g BOD/㎡/day. Suspended solids removal efficiency was between 61 and 70 percent in the Autoxidation phase at 1st stage RBC by biomass sloughing, and that of the existing RBC was between 45 and 61 percent. Removal of ammonia-nitrogen determined by varying NH₃-N loading rate showed a 85.3∼92.1 percent in the Autoxidation phase and a 67∼76percent for the existing three stage RBC process. NO₃-N level in the effluent increased with decreasing influent loading. In the determination of the kinematic coefficient, area capacity constant(P) in the first stage Autoxidation phase of RBC was 39.9gBOD/㎡·day and half velocity constant(Ks) was 306㎎/L. In the existing three stage RBC, they were 46.6gBOD/㎡·day and 467㎎/L, respectively.