The invention discloses a preparing method of waterproof and oilproof food package paper. By optimizing slurry components, after filler is pretreated and modified, a multi-layer slurry flowing box isadopted to adjust components and the ratio of all layers of slurry, and the waterproof and oilproof food package paper is prepared. The food package paper can effectively lower the dose of fluorine type oil-proofing agent, and the fluorine oilproof agent is also prevented from being in direct contact with food, and the food package paper has the advantages of being healthy and environmentally friendly.