In this paper, we first reported a novel self-humidifying composite membrane for the proton exchange membrane fuel cell (PEMFC). Cs2.5H0.5PWO40/SiO2 catalyst particles were dispersed uniformly into the Nafion (R) resin, and then Cs2.5H0.5PWO40-SiO2/Nafion composite membrane was prepared using solution-cast method. Compared with the H3PWO40 (PTA), the Cs2.5H0.5PWO40/SiO2 was steady due to the substitute of H+ with Cs+ and the interaction between the Cs2.5H0.5PWO40 and SiO2. And compared with the performance of the fuel cell with commercial Nafion (R) NRE-212 membrane, the cell performance with the self-humidifying composite membrane was obviously improved under both humidified and dry conditions at 60 and 80 degrees C. The best performance under dry condition was obtained at 60 degrees C. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions due to the presence of catalyst and hydrophilic Cs2.5H0.5PWO40/SiO2 particles. (c) 2007 Elsevier Ltd. All rights reserved.