The invention discloses a preparation method of a co-heating multi-monomer for a thermal battery. The co-heating multi-monomer is composed of a multi-monomer layer (1), a buffer layer (2) and a heating layer (3), and the preparation method comprises the preparation of a heating sheet, a buffer heating sheet, a positive electrode, a negative electrode, a diaphragm and the co-heating multi-monomer.According to the co-heating multi-monomer for the thermal battery, the multiple monomers are molded at one time, so that the mechanical strength of an ultra-thin single sheet can be improved, and theapplication of the ultra-thin single sheet process in the field of high overload is facilitated. The heating mode of a traditional thermal battery monomer is changed from one-to-one heating to one-to-many heating to optimize the structure of the thermal battery monomer, so that the efficiency is improved, and the problem that the heating sheet is not matched with the heat of the ultrathin monomeris avoided. By a rotary blade-coating mode, the ultrathin insulating layers are blade-coated between the positive electrode and the diaphragm and between the diaphragm and the negative electrode in the monomers and between the multiple monomers, and the ultrathin insulating layers and the multiple monomers form an organic entirety, so that the short circuit problem of the ultrathin monomers is avoided, and the safety of the ultrathin heat supply multi-monomer battery is greatly improved.