A new type of cross-linked polymer blend membranes consisting of poly(vinyl alcohol) (PVA), sulfosuccinic acid (SSA) and plasticizer polyethylene glycol (PEG) have been prepared and evaluated as proton-conducting polymer electrolytes. The proton conductivity (σH+) and water uptake (WU) of the membranes were investigated based on such points of view as thermal cross-linking and chemical cross-linking procedure, plasticizer effect and the content of SSA. It is found that the proton-conductivity increased with increasing the content of SSA and, reached up to 0.047 S cm-1 at room temperature with a polymer composition PVA/SSA being 1:0.5 by mass. The cross-linking modification and plasticizer addition also played an important role in σH+ and WU. The membranes were characterized by thermogravimetric analysis (TGA), and the TG results showed that the thermal stability of the resultant membranes are improved due to the chemical cross-linking and plasticizer modifications.