The invention belongs to the field of traditional Chinese medicine, and in particular, relates to a pharmaceutical composition for preventing and treating rheumatoid arthritis and a preparation methodthereof; the pharmaceutical composition includes the following raw materials: morinda officinalis, radix polygonum multiflorum preparata, herba epimedii, prepared rehmannia root, tortoise shell, morinda officinalis, eucommia ulmoides, radix dipsaci, rhizoma drynariae, radix angelicalis sinensis and Chinese yam, wherein the ratio of the total weight of morinda officinalis to the total weight of the remaining raw materials is (0.1-0.3):1, and the weight ratio of the other raw materials is 1:1. The invention provides the medicine for preventing and treating rheumatoid arthritis; the curative effect is remarkable, and the dosage of the new use is reduced as compared with that of traditional medicines. At the same time, the hepatotoxicity of the prepared medicine is greatly reduced by alcoholextraction of a part of medicinal materials creatively and then medicine preparation, the adverse reactions of clinical medication are reduced, and the medication safety is improved.