The invention discloses an emulsified capacity-increasing soy protein adhesive and a preparation method thereof. The adhesive is prepared from, by weight, 30-40 parts of soybean protein, 15-35 parts of epoxy resin, 1-3 parts of evocating agent, 10-12 parts of natural emulsion, 6-10 parts of secondary alkyl sulfonate, 6-8 parts of calcium carbonate, 6-10 parts of inorganic alkali, 10-15 parts of sodium silicate, 2-4 parts of crosslinking enhancer, 5-7 parts of polyacrylate salts, 7-9 parts of cupric sulfate and 10-15 parts of alkaline compound. The emulsified capacity-increasing soy protein adhesive enhances the added value of the soybean protein. The application process of the adhesive is environmentally friendly and hygienic, and capable of generating no toxic and harmful substances such as formaldehyde and phenol. The emulsified capacity-increasing soy protein adhesive is applicable to the fields of wooden plywood, shaving board, fiber and the like.