A now pulsewise fluidized bioreactor(biofilter)which uses immobilized microorganisms was developed for the effective biological treatment of high concentration organic wastewater. The content in the biofilter was mixed by the turbulence generated by the falling wastewater which has potential energy. Polyurethane foams were used for the support of microorganisms. In order to test the effect of mixing in the Biofilter pulse was off for 24days during the experiment. When the pulse was off, the Biofilter performance was reduced dramatically. When the raw wastewater was introduced to the Biofilter without neutralization, COD removal efficiency and biogas generation rate were almost the same in the case of neutralization. During the 400 days experiment wastewater residence time was varied from 15 day to 1 day and soluble COD removals were 90-97%. In terms of COD load polyurethane foams showed 27kg COD/㎥.d with 90% soluble COD removal. This biofilter showed more than 15 times performance in COD removal than conventional anaerobic digestion. In spite of non-neutralizing the influent wastewater the reactor kept stable operation without disturbing the performance.