Development of desalination technologies is very important for fulfilling future water demand. The objective of this research is to synthesis membrane for desalination process from cellulose acetate (CA) by blending with polyethylene glycol (PEG) and silica resulting CA/PEG/Silica composite membrane. In this study, the synthesis and characterization of composite membrane is attempt where membrane performance is investigated for reverse osmosis desalination of saline water. CA/PEG membrane with ratio 80/20 (wt%) was modified with three different particle sizes of silica: 0.007, 0.02, and 60 μm. Composite membranes were characterized for their hydrophilicity, functional groups and permeation properties. The experiment results show that hydrophilicity of CA/PEG membrane increases after the addition of silica as shown by the decreasing of contact angle and the increasing of silanol group. Hydrophilicity of composite membrane increases with the decreasing of particle size of silica. The best performance membrane is obtained by using silica with particle size of 0.02 μm.