Abstract: A novel surface deposition modified ceramic m embrane was developed to decrease the membrane pore size.Accordingly r-alumina supported membranes modified by calcium carbonate were prepared.Pore size distribution determination and SEM photographs of membranes mdicated that this modi fied membrane can reduce pore size effectively and improve the membrane separation property obviously.Comparisons of vapor permeation separation of ethanol/water mixtures between alumina membranes unmodified and those modified by CaCO_3 also supported the improvement.