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.