The invention discloses a medicament for treating diabetes, which is prepared by Chinese medicinal components such as bark of boxthorn root, ginseng, mongolian snakegourd root, schisandra berry, Chinese wolfberry, glossy privet fruit, corktree bark, rhizoma atractylodis, radix astragali, dwarf lilyturf tuber and the like according to the proportion. A preparation method for the medicament comprises the following steps: separately soaking the ginseng into water according to the weight proportion and decocting the ginseng to take filtrate, grinding one half of the Mongolian snakegourd root into fine powder and passing the fine powder through an 80-mesh sieve for later use, soaking the glossy privet fruit, the radix astragali, the corktree bark and the rest Mongolian snakegourd root into 3 times of 60 percent ethanol for 2 days, filtering the mixture to obtain filtrate, and concentrating the filtrate to obtain dry extract for later use; soaking the boxthorn root, the schisandra berry, the Chinese wolfberry, the rhizoma atractylodis and the dwarf lilyturf tuber into water, decocting the mixture, and filtering the decoction to obtain filtrate; and mixing the ginseng liquor, the ginseng powder, the Mongolian snakegourd root, the dry extract powder and the mixed filtrate, concentrating, drying and crushing the mixture, passing the mixture through a 120-mesh sieve, and sterilizing and split-charging the mixture to form instant medicament. The medicament contains pure Chinese medicinal components, and has the characteristics of reasonable formulation, simple and convenient administration, obvious treatment effect and the like; and in 89 cases of clinical application, the total efficiency reaches 92.50 percent.