Both PPO, poly(2,6-dimethyl-1,4-phenylene oxide) and SEBS, poly(styrene-ethylene-butylene-styene) were sulfonated, respectively, using chlorosulfonic acid as a sulfonating agent and 1,2-dichloroethane as a solvent. Also, Sulfonated-PPO/Sulfonated-SEBS composite membranes for PEMFC were prepared. The proton conductivity of SPPO/SSEBS(1:1) composite membrane is enhanced up to 1.3 ×10(-3) S/cm due to the increase of water swelling, the rise of compatibility between two phase, and the decrease of interfacial resistance.