The invention discloses a medicinal composition for treating hypogalactia symptom of a dairy cow and a preparation method thereof. The medicinal composition comprises the following raw materials of lythrum, radix aucklandiae, girald jasmine root, the root of three-nerved spicebush, rhizoma nardostachyos, Omei meadowrue herb, aspongopus, urtica dioica, pericarpium citri reticulatae viride, jujube, radix bupleuri, paederia scandens, nutgrass galingale rhizome, kohlrabi, lucid ganoderma, Chinese buckeye seed, calyx of singharanut, aiomatic turmeric root-tuber, woody hawksbeard root, rose, Japanese cayratia herb, semen raphani, rhizome of large-headed atractylodes, Australian cowplant root or leaf, hawthorn, hindu datura seed fruit, malt, rice-grain sprout, japanese balanophora, dangshen, turnip, Chinese yam and ficus pumila fruit. The medicinal composition disclosed by the invention has the benefits that the medicinal composition is mainly used for nourishing spleen and regulating qi and is assisted for reinforcing qi and enriching blood; the immunity of the dairy cow is improved, the lactation yield, the milk-fat percentage, the milk protein content, the lactose content and the content of dry substances in the milk can be improved; the breast plump and normal development of a nipple are promoted; milk is full, and the phenomenon of sudden decrease of appetite or inability to eat is avoided; the medicinal composition has the advantages of few toxic or side effects and remarkable effect; in addition, normal growth of mammary gland and other organs of the dairy cow can be better guaranteed.