The removals of nitrogenous component(NH4(+)) and COD from the synthetic waste water have been investigated in a three-phase circulating fluidized-bed reactor whose diameter is 0.102 m. Activated sludge which is used for waste water treatment at the Wonchun-dong in Daejon has been employed as a microorganism. Filtered compressed air and synthetic waste water have been used as a gas and a liquid phase, respectively. Anion polymer resin whose diameter is 0.4 mm has been used as a fluidized solid substrate, at which microorganism has been adhered. Effects of initial concentration of NH4(+) in the waste water and substrate holdup on the efficiency as well as amount of the removal of NH4(+) and COD have been discussed. The reaction temperature, pH and concentration of dissolved oxygen have been maintained at 20 ℃, 7 and 6-7 mg/L, respectively. It has been found, from the results of this study, that the three-phase circulating fluidized-bed bioreactor can be utilized as an effective scheme to remove the NH4(+) and COD in the waste water continuously. The use of substrate particle with microorganism adhered at its surface can increase the removal efficiency of NH4(+) and COD considerably. The removal efficiencies of NH4(+) as well as COD have increased with increasing the holdup of substrate with active microoranism, but decreased with increasing the initial concentration of NH4 (+) in the waste water. The efficiency has been found to be closely related to the combination of the initial concentration of NH4(+) and substrate holdup in the reactor; the optimum amount of substrate has been dependent upon the initial concentration of NH4(+) in the waste water.