A novel sulfoalkoxylated diamine, 2,2'-bis(3-sulfopropoxy) benzidine (2,2'-BSPB) was successfully synthesized and the sulfonated polyimide was prepared from this diamine and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). The resulting polyimide membrane displayed high proton conducting performance and excellent water stability, indicating potential application for polymer electrolyte fuel cells.