A proton exchange membrane modified with montmorillonite (NMT) was prepared by introducing perfluorosulfonylfluroride resin into the interlayer of MMT at high temperature and high pressure. The intercalating structure was analyzed by wide-angle X-ray diffraction (XRD), and the results showed that the polymer was indeed intercalated into the interlayer of the modified montmorillonite (m-MMT) matrix without destroying the microstructure of the matrix by largely increasing the d-spacings of m-MMT. SEM analysis on the surface and cross-section of these composite membranes shows that the MMT nanoparticles are dispersed in the membrane uniformly. This composite membrane reveals excellent water retention and conductance at high temperature. The composite membrane was evaluated in a single cell, and the results show that the performance of composite membrane is higher than that of pure Nafion membrane at high temperature especially without external-humidification. (C) 2008 Wiley Periodicals, Inc.