The invention discloses a process for preparing composite sulfonated membranes with IPN structures, which is characterized by utilizing dehydration cross-linking agent to lead IPN structures between two polymers to prepare polymers with IPN structures, obtaining IPN composite sulfonated proton exchange membranes through a solvent casting method, adjusting mole ratio of sulfonate and non-sulfonatethrough sulfonated dihalides, non-sulfonated dihalides and compounds containing dyhydroxyl, or changing structures of the sulfonated dihalides, the non-sulfonated dihalides and the compounds containing dyhydroxyl, and obtaining different types of straight-chain sulfonated compounds via polymerization reaction. The different types of straight-chain sulfonated compounds form proton polymers via proton exchange, and IPN composite sulfonated polymer membranes can be obtained by the proton polymers via high-temperature casting treatment under action of the dehydration cross-linking agent. The process is simple in synthetic process and controllable in sulfonation degree and cross-linking degree, and does not have problems of component separation caused by other compound methods.