Cellulose acetate membrane has been applied to reverse osmosis for desalination due to chlorine tolerance and biofouling resistance. Since it requires optimized synthesis condition for application, we investigated the effect of different conditions on membrane performances. It was found that polymer concentration, solvent ratio, and evaporation time were critical to determine membrane selectivity and permeability. Based on the study, optimized conditions were obtained, which were 14 wt% of polymer concentration, 1:2.(of ratio of 1,4-dioxane to acetone, and 30 s of evaporation time. Further, functionalized multi-walled carbon nanotubes (MWCNTs) were applied to the optimized bare membrane in order to enhance the performances. The composite membranes were characterized by fourier transform infrared spectroscopy, scanning electron microscopy, and contact angle measurement. It was found that the MWCNTs influenced the morphology and surface chemistry of the membrane. This study could contribute to develop a commercial composite RO membrane with nanomaterial for desalination application.