In order to increase both of the water uptake and conductivity, the proton exchange membranes were fabricated by sulfonated poly(ether ether ketone) (SPEEK) doped with varied contents of silica sulfuric acid (SSA) which is obtained by treating SiO2 nanoparticles with more volatile SO2Cl2. SEM images of the composite membranes show that SSA nanoparticles are dispersed within the membranes uniformly, indicating the good organic compatibility of SSA particles. TEM images show that the composite membranes have improved ionic clusters distribution. The water uptakes of the composite membranes in water and under low relative humidities are all higher than that of the pristine SPEEK membrane. The addition of SSA enhances the conductivity obviously. The composite membrane containing 5wt.% SSA exhibits the highest conductivity of 0.13 Scm(-1) at 80 degrees C, approximately 18.6% higher than that of the pristine SPEEK membrane and 8.6% higher than that of Nafion117. The composite membranes also show good thermal stability. These results imply the potential application of the SPEEK/SSA composite membranes as improved PEMs in PEMFC. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.