The　start-up　characteristics　of　membrane　bioreactor　(MBR)　process　(HRT:　0.5h)　with　powdered　activated　carbon　(PAC)　as　the　support　for　bacterial　growth　was　investigated　for　drinking　water　treatment.　The　results　showed　that　when　ammonia　nitrogen　was　concerned,　the　natural　start-up　finished　accomplished　within　9　days　after　the　initially　difficult　period　(20d).　The　MBR　exhibited　the　stable　removal　of　NH3-N　with　an　average　efficiency　of　89.4%　after　the　maturity　of　nitrosomonas　group　in　the　bioreactor.　However,　nitrite　nitrogen　was　observed　to　accumulate　in　the　MBR　effluent　during　the　maturation　of　nitrosomonas　group　and　the　start-up　accomplishment　lagged　6　days　behind.　While　considering　the　organic　pollutants　removal,　due　to　the　synergistic　effects　of　PAC　adsorption　and　biodegradation,　there　was　no　clear　indication　for　the　maturity　of　heterotrophic　bacteria.　And　the　stable　removal　for　organic　matter　was　achieved　by　the　MBR　during　the　experiments.　The　average　removal　efficiency　of　TOC,　CODMn,　DOC　and　UV254　were　26.4%,　30.7%,　20.4%　and　21.7%　on　average,　respectively.