The invention discloses a preparation method of a milk protein-anionic polysaccharide emulsification stabilizer, and solves the problems that the conventional emulsification stabilizer is poor in stabilizing effect and short in shelf life. According to the technical scheme, the milk protein-anionic polysaccharide emulsification stabilizer comprises the following raw materials in parts by weight: 0.3-0.6 part of milk protein, 0.3-0.6 part of anionic polysaccharide and 75.7-87.3 parts of water; the preparation method comprises the following steps: dissolving the milk protein into water, adjusting pH to 7, then denaturing at the high temperature of 65-95 DEG C, cooling to 15-25 DEG C, then adjusting pH to 4-8, adding the anionic polysaccharide, stirring till the anionic polysaccharide is dissolved, and obtaining the milk protein-anionic polysaccharide emulsification stabilizer. The milk protein-anionic polysaccharide emulsification stabilizer is good in mouth feel; the raw materials are easy to obtain; the milk protein-anionic polysaccharide emulsification stabilizer is safe and healthy, has a good emulsifying effect, and can effectively improve the stability of milk beverage to prolong the shelf life of a product.