The invention discloses a formula for preparing Qingtang capsules and a method thereof. The formula provided by the invention comprises the following components: 50g of root of kudzu vine, 50g of balsam pear, 50g of corn silk, 25g of guava leaf, 20g of Tuber of Dwarf Lilyturf, 20g of sea-tangle, 15g of wolfberry, 10g of malt, 9g of rehmanniae radix, 6g of radix paeoniae rubrathe and 0.03g of melbine. The method for preparing the Qingtang capsules comprises the following steps: uniformly mixing a water extract of ten traditional Chinese medicines and a fine melbine powder to prepare granules and putting the granules into capsules. According to the invention, root of kudzu vine, balsam pear, corn silk, guava leaf, Tuber of Dwarf Lilyturf, sea-tangle, wolfberry, malt, rehmanniae radix, radix paeoniae rubrathe and melbine are adopted to prepare the Qingtang capsules. The mouthfeel of the Qingtang capsules is improved, and it is convenient for patients with diabetes to take. Effective medicines for reducing blood sugar, including root of kudzu vine, wolfberry, rehmanniae radix, balsam pear, guava leaf, radix paeoniae rubrathe, melbine and the like, are adopted; and a plurality of components are combined together. The formula has little side effect, has effects of nursing one's health, strengthening the body resistance and mildly reducing blood sugar, and is safe and effective. The method is simple and convenient to use. A convenient approach is provided for the treatment of diabetes.