The Pervaporation technique using membrane has been found applicable to liquid mixtures that are difficult to separate or purify by the distillation. Especially, it was found that an azeotropic mixture or a close-boiling mixture could be separated by using the difference in solubility of the solvents for the membrane. Therefore, in this paper, the permeation and separation characteristics of cellulose acetate(C.A.), cellulose (Cell.), and carboxymethylcellulose(CMC) membrane with azeotropic mixtures such as dioxane/H2O and n-propano1/H2O ware investigated and compared with each other according to the separation conditions including temperature, concentration of azcotropic mixtures, and separation time. Specially designed pervaporation apparatus was used to forecast permeate phenomenon of cellulosic membrane at the beginning stage. The permeate concentration was generally increased at the beginning stage, but led to permeate equilibrium as the experiment time passed. Stable fluxes were reached after 2 hours of experimental runs, which were measurers by weighing the condensed products. The temperature dependence of the permeation rate was expressed by Arrhenius-type relationships. The separation characteristics of the cellulosic membranes were very steady state at experimental temperature range. The experimental results were indicated that the cellulosic membranes wert very effective for a selective separation of water from azeotropic mixtures by pervaporation technique.