Sulfated　chitosan　(SCS),　a　typical　amphoteric　polyelectrolyte,　was　prepared　through　a　homogeneous　method,　and　via　coating　and　cross-linking　methods,　the　sulfated　chitosan/polysulfone　(SCS/PSF)　nanofiltration　membranes　were　prepared　by　using　SCS　aqueous　solution　as　casting　solution　of　the　active　layer,　the　glutaraldehyde　as　cross-linking　agent　and　the　polysulfone　ultrafine　(PSF　UF)　membrane　as　support　membrane,　respectively.　The　surface　and　cross-section　morphologies　of　the　prepared　membrane　were　characterized　by　environmental　scanning　microscopy　(ESEM).　The　effects　of　the　composition　of　casting　solution　forming　active　layer　and　the　preparation　techniques　of　the　composite　membrane　on　the　rejection　performance　of　the　prepared　membranes　were　investigated.　At　13-15°C　and　0.30　MPa,　using　the　prepared　SCS/PSF　composite　membrane,　the　rejection　ratio　of　Na2SO4　and　NaCl　solutions　with　concentrations　of　1000　mg·L-1　are　91.2%　and　48.5%,　respectively,　while　the　permeate　fluxes　of　them　are　3.2　and　6.7　kg·m-2·h-1　respectively.　Moreover,　the　rejection　ratios　of　the　inorganic　electrolyte　solutions　are　in　the　orders　as　follows:　Na2SO4　＞　NaCl　＞　MgSO4　＞　MgCl2.　It　suggests　that　the　active　layer　of　the　composite　membrane　has　a　negative　surface　charge　distribution　caused　by　the　absorption　of　anions　from　the　electrolyte　solution,　and　this　charge　distribution　determines　mainly　the　rejection　performance　of　the　composite　membrane.