Composite collodion membranes modified by the addition of different amounts (0-1.0 wt.%) of NaClO4 were prepared keeping a fixed concentration of perfluorobenzoic acid (PFBA) within membrane. The composite membranes indicated relatively high cation transport number and proved to be available as a cation exchange membrane. From volume flow and salt flow studies across membranes, the filtration coefficient, L-p, and the salt permeability, omega, were estimated as a function of added NaClO4. As a result, while L-p increased gradually in proportion to the amounts of NaClO4, omega indicated an abrupt increase of around 0.2 wt.% of NaClO4. The similar critical behavior was found in the measurement of membrane conductance and the result assured the critical change in omega. Furthermore, based on the above membrane parameters such as L-p, omega and Lambda(m), the frictional consideration regarding the interactions between water and membrane matrix or between salt and membrane matrix was done and the transport properties were discussed in relation to the membrane structure.