The invention discloses a traditional Chinese medicine for treating diabetes mellitus. The traditional Chinese medicine is prepared from, by weight, radix ginseng rubra, dried rehmannia roots, prepared rehmannia roots, sphallerocerpus gracilis, radix pseudostellariae, the fruits of Chinese wolfberry, the roots of red-rooted salvia, pulp of dogwood fruits, Chinese yam, rhizoma atractylodis, radices trichosanthis, cortex lycii radicis, rhizoma alismatis, cortex acanthopanacis, the roots of straight ladybell, radix ophiopogonis, the fruits of Chinese magnoliavine, goldthread roots, endothelium corneum gigeriae galli, radix polygonati officinalis, astragalus membranaceus, angelica sinensis, cortex cinnamomi, morinda officinalis, lucid ganoderma, taraxacum mongolicum, radix paeoniae alba, achyranthes roots, polygonatum kingianum, flos carthami, the seeds of Chinese dodder, epimedium gradiflorum morr, polygonum multiflorum, rhizoma atractylodis macrocephalae and parasitic loranthus. Starting with regulating Yin deficiency and dryness heat, Qi and Yin deficiency and Yin and Yang deficiency of patients with the diabetes mellitus, the traditional Chinese medicine can effectively control the blood glucose level of the patients with the diabetes mellitus to be within a normal value range, is free of side effects and has the function of nourishing Yin deficiency.