The invention discloses a high-strength food bag and a preparation method thereof. The preparation method comprises the following steps: (1) mixing raw materials, and carrying out thermal treatment, so as to form a mixture; (2) carrying out extrusion molding on the mixture, so as to prepare a plastic film; and (3) processing the plastic film into the high-strength food bag, wherein the raw materials include polyethylene terephthalate, o-phenylphenol, fillers, a coupling agent, natural silk, asbestos, white carbon black, fructus gleditsiae, fruticose dracaena leaves, diatomite, bran, hemp palm, bamboo clothing, starch, rhizoma alpiniae officinarum, rhizoma cimicifugae, clove and flos magnolia. The high-strength food bag prepared by virtue of the preparation method has excellent mechanical strength and mould resistance, and meanwhile, the raw materials in the preparation method are easily available, so that the industrial volume production of the high-strength food bag can be realized.