The blend membranes were satisfactorily prepared by coagulating a mixture of O-carboxymethylated chitosan (CM-chitosan) and alginate in aqueous solution with 5 wt % CaCl2, and then by treating with 1 wt% HCI aqueous solution. Their structure and miscibility were characterized by scanning electron micrograph, X-ray diffraction, infrared spectra, differential thermal analysis, and atomic absorption spectrophotometer. The results indicated that the blends were miscible, when the weight ratio of CM-chitosan to alginate was in the range from 1:1 to 1:5. The polymers interpenetration including a Ca2+ crosslinked bridge occurred in the blend membrane, and leads to high separation factor for pervaporation separation of alcohol/water and low permeation. The tensile strength in the wet state (sigma(b) = 192 kg cm(2) for CM-chitosan/alginate 1 : 1) and thermostability of the blend membranes were significantly superior to that of alginic acid membrane, and cellulose/alginate blend membranes, owing to a strong electrostatic interaction caused by -NH2 groups of CM-chitosan with -COOH groups of algic acid.