The present invention relates to a high-temperature proton exchange membrane fuel cell, and in particular to a preparation method of a triazole-based ionic crystal / polymer composite film. The method uses a high-temperature dipping method to immerse the triazole-based ionic crystal into a polymer substrate, so as to prepare a composite film. The prepared film has the advantages of high conductivity and low permeability. The composite film prepared by the present invention has potential application prospect in high-temperature exchange membrane fuel cell.