Fouling characteristics were studied in the continuous operation of pilot-scale submerged membrane bioreactor (SMBR) for 120days. The ratio of flux decline (J/Jo) varied with suction pressure and backwash cycle. Fouling decreased significantly while flux increased when the reactor operated on suction at 300㎜Hg for 5 minutes followed by backwash for 1 minute. Fouling was affected by MLSS and SS in the influent seriously. In particular, influent SS such as cellulose material, hair and red pepper powder caused most of resistance in the beginning of operation, attaching the surface of membrane and blocking the pores. Therefore, pretreatment was required to remove SS. It was observed that SMBR was stable to high and shock loadings, as the removal efficiencies of COD and SS were maintained 97% and 100% when influent characteristics changed irregularly. Because the cake resistance caused by ECP was the major resistances caused by MLSS and resistance varied with the ratio of protein and carbohydrate even in constant ECP from previous study, total ECP and the ratio of ECPp to ECPc must be monitored to keep the flux stably in SMBR.