The proton conductivity of chemically cross-linked composite membranes consisting of poly(vinyl alcohol) (PVA) and silicotungstic acid (STA) prepared by solution casting as proton-conducting polymer electrolytes was investigated as a function of blending composition, cross-linking density, and temperature. The conductivity mechanism was investigated by using Impedance spectroscopy in the region between 40 Hz and 10 MHz. Membranes were also characterized by FTIR to confirm the cross-linking reaction and differential scanning calorimetry (DSC) to assess the thermal stability. Membrane swelling decreased with increase in cross-linking density accompanied by improvement in mechanical properties. The proton conductivity of the membranes was of the order of 10-3 S/cm and showed similar resistance to methanol permeability as Nafion 117 under the same measurement conditions.