The invention belongs to the technical field of food processing, and particularly relates to a preparation method of a health-care beverage having the function of assisting in reducing blood pressure.The preparation method comprises the following steps of: mixing edible soybean meal powder with potato extracts, adding neutral protease for enzymolysis, and then performing filtering to obtain soybean protein enzymatic hydrolysate; uniformly mixing celery juice with the soybean protein enzymatic hydrolysate to obtain mixed liquid; adding 2% glucose to the mixed liquid, performing stirring to enable the glucose to dissolve, then performing sterilization, performing cooling and performing fermentation with black fungus strains to obtain black fungus fermentation liquid; fermenting the black wood ear fermentation liquid with lactobacillus plantarum to obtain lactic acid bacteria fermentation liquid, and refining the lactic acid bacteria fermentation liquid through a mycelium colloid mill toobtain nutrient slurry; and filtering the nutrient slurry, performing blending, performing sealing, and performing sterilization to obtain finished products. The health-care beverage is rich in various functional components, and high in activity of apigenin, soybean peptides, gamma-aminobutyric acid and the like, and has the function of assisting in reducing blood pressure.