The invention discloses a preparation method for dampproof food wrapping paper. The method comprises the steps that firstly, a silane coupling agent is adopted for modifying nanometer titania, and modified nanometer titania is prepared; then, chitosan is added to an acetic acid solution and stirred until chitosan is completely dissolved, modified nanometer titania, glycerinum, modified starch andsodium laurate are added while stirring is conducted, stirring continues, and a dampproof agent is obtained; a surface sizing agent is added into the dampproof agent, the pH is adjusted to 6-7, raw paper is coated with the mixed solution and dried, and the dampproof food wrapping paper is obtained. According to the preparation method, the coupling agent is adopted for modifying nanometer titania,cooperating with chitosan and serving as an antimicrobial agent, in combination with modified starch and sodium laurate, the dampproof antimicrobial agent is prepared, the influence of moisture on food quality can be effectively resisted, growth of microorganisms can also be inhibited, and the shelf life of food is prolonged.