The invention relates to a method for preparing a mulberry leaf beverage by virtue of enzymatic transformation of flavonoids from mulberry leaves, and the method comprises the following steps: extracting a mulberry leaf leaching solution and performing enzymatic transformation: mixing the fresh mulberry leaves (kg) with purified water (L) in a weight-to-volume ratio of (1:5)-(1:50), then leachingat the temperature of 60-100 DEG C for 1-12 hours so as to get the mulberry leaf leaching solution, mixing the mulberry leaf leaching solution with glycosidase for performing enzymatic hydrolysis reaction at the reaction temperature of 20-70 DEG C for 10-72 hours and further getting enzymatic hydrolysate of the mulberry leaf leaching solution after the reaction is completed, wherein the basic composition and the formula of the mulberry leaf drink are as follows: in 100kg of the product, the product contains 10kg-15kg of the enzymatic hydrolysate of the mulberry leaf leaching solution, 4kg-7kgof sucrose, 0.10kg-0.50kg of citric acid, 0.125kg of vitamin C, 0.01kg of essence, 0.5kg-1.5kg of honey and the balance of the purified water. The mulberry leaf beverage has the advantages of high degradation rate of flavonoid glycosides from the mulberry leaves, fresh fragrance, clarity, transparency, bright color, sweet, acid, moist and cool taste, mellow and long aftertaste and excellent mouthfeel.