Provided is a fabrication method for a composite planar pH sensor modified by graphene film including: slotting into substrate, setting copper foil on both sides, and setting leads on the copper foil; coating graphene film on the copper foils using micro mechanical stripping method to form the first graphene film and the second graphene film; depositing Sb layer and Sb2O3 layer successively on the first graphene film by magnetron sputtering method, and coating Nafion™ perfluorinated sulfonic acid membrane on the Sb2O3 layer by spin-coating method to fabricate pH working electrode; depositing Ag layer on the second graphene film and dipping in FeCl3 solution to form AgCl layer; coating the third graphene film on the AgCl layer to fabricate reference electrode. The composite planar pH sensor modified by graphene film may be used in pH measurement for solid, semisolid, mash and solution samples.