The　effect　of　carbon　nanotubes　(CNT)　modification　on　ultrafiltration　membrane　fouling　control　was　explored.　Three　kinds　of　base　membrane　were　chosen　in　the　study:　20　kDa　polysulfone　(PS)　membrane,　20　kDa　and　100　kDa　polyethersulfone　(PES)　membrane.　Besides,　the　effect　of　pre-ozonation　on　the　three　CNT　modified　membranes　for　fouling　alleviation　was　further　studied.　CNT　modification　presented　antifouling　properties　at　the　beginning　of　filtration,　while　the　recoverability　of　the　CNT　modified　membranes　are　relatively　lower　as　for　the　blocking　of　CNT　layer　by　foulants.　Pre-ozonation　with　a　lower　ozone　concentration　(0.25　mgO(3)/mgDOC)　did　not　efficiently　alleviate　the　fouling　of　CNT　modified　membranes.　With　the　ozone　concentration　increased　to　0.81　mgO(3)/mgDOC,　the　CNT　modified　membranes　exhibited　their　higher　antifouling　properties.　Water　quality　analysis　results　showed　that　CNT　modification　presented　a　higher　capture　ability　for　the　humic-like　and　protein-like　substances.　After　pre-ozonation,　more　organic　materials　could　be　retained　in　the　interior　of　CNT　layer,　which　decreased　the　fouling　of　base　membranes　and　increased　the　permeate　quality　as　well.　Base　membrane　with　large　molecular　size　cut-off　is　more　helpful　for　the　synergistic　effect　of　pre-ozonation　and　CNT　modification.