The invention discloses a paper-like spontaneous heating film and a preparation method thereof. The spontaneous heating film comprises spontaneous heating metal powder and a fiber carrier. The spontaneous heating metal powder is evenly distributed in the fiber carrier and forms a paper-like film with the fiber carrier together. The fiber carrier comprises fibers and activated carbon powder. The spontaneous heating metal powder is a mixture of iron powder and aluminum powder, wherein the content of the aluminum powder is 0.05%-50% by mass. The paper-like spontaneous heating film is arranged according to the surface density of 100-1000 g/m<2>. The fibers include paper fibers, wood fibers, hydrophilic chemical fibers, carbon fibers and carbon nanofibers. The metal powder, the fibers, activated carbon powder and an ionic surfactant are dissolved in water and are stirred evenly, then industrial salt is added and concentration is performed; and then a substrate is coated with the thick slurry by a uniform coating method or a roll pressing method, and after drying is performed, the paper-like spontaneous heating film is obtained. The fibers are used as the carrier, diffusion channels areprovided for oxidizers of the metal powder, the energy efficiency is improved and the metal powder is prevented from falling off.