Abstract: Objective: The effect of the Semiliquidambar cathayensis root on adjuvant-induced arthritis in rats was investigated, and the active extract and the chemical components in the root were determined. Methods: Rheumatoid arthritis model rats were divided randomly into five groups. Changes in the degree of swelling of the left hind feet and arthritis indexes were recorded. The thymus and spleen indexes of the rats were calculated after treatment. Changes in the COX-2 and 5-LOX levels in peripheral blood monocytes (PBMC) and serum IL-6, IL-1β, TNF-α, and IL-10 levels were measured. The pathomorphological changes to the rat ankle joint were observed by hematoxylin-eosin staining(HE staining). The effects of four different solvent fractions of an alcohol extract of the Semiliquidambar cathayensis root on changes to the left hind foot swelling volume and arthritis index in rats were investigated. The effective parts were analyzed qualitatively by UPLC-Q-TOF-MS. Results: The degree of foot swelling, arthritis indexes, and spleen indexes were reduced significantly in the positive drug group (1.6 g/kg) when compared with the model group. The COX-2 and 5-LOX levels in PBMC and IL-6, IL-1β, and TNF-α decreased significantly. The IL-10 serum level increased significantly. The infiltration of inflammatory cells in the joint tissue decreased, and morphology improved. The swelling volume of lateral feet and arthritis index in rats were reduced significantly in the n-butanol fraction from total alcohol extracts of the Semiliquidambar cathayensis root. One-hundred and four chemical components were identified from the n-butanol fraction, including organic acids, sugars and glycosides, flavonoids, quinones, and coumarins. Conclusion: The Semiliquidambar cathayensis root had an apparent protective effect on adjuvant arthritis-immunized rats. This root would have broad prospects in developing antiarthritic drugs and functional food.