||A successful fuel cell membrane has to have good proton conductivity, chemical stability, and mechanical stability. Therefore, several engineering plastics are sulfonated for the fuel cell membrane materials because they have mechanical strength and in many cases some chemical stabilities. Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is known to have a high glass transition temperature, and is known to be miscible with polystyrene regardless of the PPO’s molecular weight due to a favorable exothermic interaction. In this research, a highly sulfonated sPPO was synthesized by post-sulfonation method which utilizes trimethylsilyl chlorosulfonate as the sulfonating agent. And the sPPO was blended with a sulfonated polystyrene copolymer which contains a small amount of azide groups. The blend membrane was crosslinked, and the membrane characteristics such as water uptake, proton conductivity, and methanol permeability were measured.