The use of ultrafiltration (UF) is receiving more attention for drinking water treatment, but its fouling remains a problem. Reservoir water was selected as raw water during pilot study. Worldwide drinking water reservoirs may contain algae, which pose a threat to drinking water treatment. UF membrane has been recognized that it can remove algae for its nominal pore sizes. The algal cells cumulate on membrane surface, and the secretion released by them would cause transmembrane pressure increases or flux decreases. Also, conventional backwashing could not satisfy with the need of flux recovery. Frequent chemical cleaning may shorten the membrane unit's service life. The best available technology for UF membrane system during algae bloom should be inactivating algae and removing them before they are fed into UF membrane. The objective of this study was to investigate the effect of pretreatment by permanganate/chlorine on UF membrane operation for controlling algae fouling. It was found that combined use of permanganate and chlorine could reduce the rate of UF membrane fouling. Permanganate and chlorine could be in synergistic action in inactivating algal cell. The intermediate of permanganate, hydrous manganese dioxide (MnO2) could adsorb on algal cells depending on its strong specific surface area. In addition to permeate water quality, specific flux (at constant TMP) and TMP (at constant flux) of UF membrane also demonstrated that pretreatment could improve UF membrane system.