A feasibility of zeolite reuse by thermal treatment of excess sludge in zeolite added activated sludge(AS) was evaluated. Optimal regeneration conditions for NH4(+)-N ion exchange property of zeolite in excess sludge was decided at 500 ℃ of temperature for 1 h, which corresponded to 88% of regeneration efficiency. The reactor of zeolite dose, run in two models according to zeolite dosed(model I-original zeolite dose and model II-regenerated zeolite addition), was compared to conventional AS under equivalent operating condition. The concentration of zeolite in aerobic basin was maintained at 4,000 mg/l, and the average concentrations of COD, T-N and T-P in influent were 150 mg/l, 40 mg/l and 3 mg/l, respectively. Besides, influent NH4(+)-N concentration was increased from 40 mg/l to 90 mg/l and 135 mg/l, separately, in 88 d and 96 d of operating duration (model II). Though the removal efficiency in soluble organic compounds was similarly observed between two reactors, the removal efficiency of total organic compounds in AS of zeolite addition was improved by 28%, compared to conventional AS. The result was attributed that zeolite progressed sludge settling property followed by enhancing SS(Suspended Solids) concentration from 2 to 12 mg/l in effluent. While, AS reactor with zeolite addition averagely showed high nitrification efficiencies of 74% and 76% in model I and II, respectively, although conventional AS averagely revealed only 58% of nitrification efficiency. As a consequence of evaluating a mutual relationship among nitrification rate, microbial concentration and nitrification efficiency, the enhancing nitrification in AS of zeolite dose was ascribed to high concentration of nitrifying bacteria. In addition, at 90 mg/l and 135 mg/l of increased NH4(+)-N concentration, the reactor with zeolite application showed 16 to 20% of nitrification efficiency higher than that in conventional AS, and hereby it was validated that nitrification of high activity was accomplished in AS with regenerated zeolite dose.