The invention discloses a traditional Chinese medicine for preventing and treating Alzheimer disease and a preparation method thereof. The traditional Chinese medicine is prepared from the following raw materials in parts by weight: 12-16 parts of prepared fleece flower root, 8-12 parts of ginseng, 9-13 parts of rhizoma acori graminei, 5-9 parts of coptis and 6-10 parts of chuanxiong rhizome. The traditional Chinese medicine can be prepared into granules, capsules, soft capsules, dissolved medicines, dripping pills and soft extracts, has the advantages of simple manufacturing process and low cost, is completely prepared from natural plants, does not contain hormones, has no addition of pigments and other chemical synthetics, and does not have toxic side effects on human bodies after being continuously used. The traditional Chinese medicine contains various effective components such as flavones, saponins, phenolic acids, alkaloids, polysaccharides and the like capable of being easily absorbed by human bodies, can be effectively used for nourishing the kidney and invigorating the brain, replenishing qi and dissolving turbidity and promoting blood circulation and eliminating toxicity, and is suitable for treating deficiency of the kidney, mild cognitive impairment caused by obstruction of the orifices by blood stasis, Alzheimer disease and the like.