A series of sulfonated polystyrene-b-poly(ethylene-b-butylene)-b-polystyrene (S-SEBS) membranes with high water permeability and then-no-mechanical stability were prepared to estimate the membrane utility for heating/ ventilation/air conditioner (HVAC) system. The sulfonation degrees of membranes were controlled by the contents of sulfonating reagent (acetyl sulfate) added. Proton conductivity and water permeation properties of the membranes increased with increasing sulfonation degree. And gas permeation properties were measured to investigate effect of sulfonation of the membranes on permeation properties. Membrane stability with increasing sulfonation degree was also studied.