For the pervaporation separation of methyl t-butyl ether (MTBE)/methanol mixtures, polyion complex (PIC) composite membranes, composed of sodium alginate (SA) and chitosan, were prepared by alternating electrostatic adsorption of SA and chitosan on polysulfone-supporting membrane. The pervaporation experiments were carried out under various preparation and operating conditions. The results showed that the prepared membranes strongly exhibited a methanol permselectivity for the MTBE/methanol mixtures, and moreover, through certain of these membranes, only methanol was permeated. Also, by increasing the chitosan content in the reaction solution, the permeation rates and MTBE concentrations in the permeate decreased gradually because of an increase in the ionic complexation between SA and chitosan. Furthermore, raising the pervaporation temperature led to an increase in both the permeation rate and the separation factor.