Chitosan　and　quaternized　chitosan　are　employed　to　enhance　the　rejection　of　Cr(VI)　by　ultrafiltration　membrane.The　influences　of　pH,the　operating　pressure,the　loading　ratio　and　the　grafting　rate　of　quaternary　ammonium　groups　on　the　rejection　performances　are　studied.It　suggests　that　both　pH　and　loading　ratio　are　major　factors　to　influence　the　rejection　to　Cr(VI).At　the　same　operating　condition,the　removal　efficiency　of　ultrafiltration　membrane　enhanced　by　quaternized　chitosan　is　better　than　that　enhanced　by　chitosan.The　characteristics　of　the　hydrophilic　gel　layer　on　ultrafiltration　membrane　affects　the　permeate　flux　and　rejection　performances　in　a　certain　degree.Due　to　better　hydrophilicity,quaternized　chitosan　significantly　increases　the　rejection　of　Cr(VI)　and　permeate　flux　of　ultrafiltration　membrane　in　comparison　with　chitosan.The　rejection　of　Cr(VI)　is　increased　significantly　with　the　increase　of　the　grafting　rate　of　quaternized　chitosan.The　rejection　is　increased　from　65.2%　to　75.5%　as　the　grafting　rate　rises　from　109%　to　530%,respectively.　©　2016,　China　National　Chemical　Information　Center.　All　right　reserved.