Sulfonated graphene oxide (SATS-GO) was mixed with sulfonated poly(arylene ether sulfone) as an inorganic/organic filler to fabricate composite membranes for proton exchange membrane fuel cells (PEMFCs). SATS-GO could be synthesized by the reaction of graphene oxide (GO) and sulfonated poly(arylene thioether sulfone) (SATS). The SPAES/SATS-GO composite membranes were obtained by typical solution casting method. As a control group, pristine GO composite membrane was also prepared to study the effect of SATS-GO. SATS-GO compsotie membranes showed improved proton conductivity and physicochemical properties compared to pristine SPAES membrane. SPAES/SATS-GO-2.0 composite membrane especially showed the largest proton conductivity value of 4.63 mS cm-1 at 80 ℃ and 40% RH.