Nanocomposite polymer electrolyte membranes comprising a crosslinked polymer blend of poly(vinyl alcohol)/poly(styrene sulfonic acid-co-maleic acid) (PVA/PSSA-co-MA) and fumed silica nanoparticles were prepared for direct methanol fuel cell (DMFC) applications. Silica nanoparticles could be incorporated well uniformly in the completely miscible system, which can form a three-dimensional network structure to achieve the enhancement of mechanical properties as well as the additional reduction of methanol permeability. The optimized proton conductivities and methanol permeability of the PVA/PSSA-co-MA membrane with silica nanoparticles of 10 wt.% were 0.0482 S cm-1 at room temperature and 5.78 × 10-7 cm2 s-1 at the methanol concentration of 40% (w/w), respectively.