A　series　of　carboxymethyl　cellulose　sodium　composite　nanofiltration　membranes　were　prepared　through　the　method　of　coating　and　cross-linking.　Effects　of　the　preparation　techniques　and　the　operating　conditions　on　the　rejection　performance　of　the　resulting　membranes　were　investigated,　respectively.　It　suggested　that　the　resulting　composite　NF　membrane　with　excellent　rejection　performance　should　be　prepared　through　a　certain　preparing　technology.　Attenuated　total　reflection　infrared　spectroscopy　and　atomic　force　microscopy　were　employed　to　characterize　the　resulting　membrane.　The　rejection　of　this　kind　of　negatively　charged　membrane　to　the　electrolyte　solutions　decreased　in　the　order　of　Na2SO4,　NaCl,　MgSO4,　and　MgCl2.