Developing low-cost, high-performance novel proton exchange membranes (PEMs) to replace Nafion is of great significance. By grafting quaternary ammonium cations onto the side chains of polybenzimidazole (PBI), abundant charge carriers and proton hopping sites are provided for proton transport, accelerating proton migration and thereby enhancing the proton conductivity of the composite membranes. Meanwhile, polyoxometalates (POMs) are introduced through electrostatic interactions and their exceptional proton-conducting properties further improve the proton conductivity of the composite membranes, with the maximum proton conductivity reaching 0.123 S cm^-1. This work demonstrated that POMs-based materials can serve as excellent proton carriers, expanding the selection of active materials in composite membranes and providing new theoretical references for the fabrication of novel proton exchange membranes.