Abstract: A new inorganic and organic composite membrane with above 60% inorganic materials was developed in this paper. The composite membrane possessed good sulfuric acid resistance because part of inorganic materials crosslinked in drying. After being dried at 80℃ for 30min, the membrane could restore its original weight in moisture air, and the chemically combined water in the membrane dissolved until to 120℃,therefore the membrane showed excellent proton conductivity even in dry air with relative humidity below 40%. The conductivity was 1.14×10^-2 S/cm at room temperature and increased to 2.81×10^-2S/cm at 60℃. Without any humidification, the power density of this composite membrane was twice that of Nafion117 at room temperature.