Abstract: Five crystalline substances were isolated from the roots of Aristolochia kwangsiensis Chun et How ex CF Liang, four of them were identified as allantoin, aristolochic acid, β-sitosterol and 3,4-methylenedioxy-6,8-dimethoxy-1-methyl ester phenanthrene.Crystal V was yellow needle, melting at 238～240℃ (dec.), with the empirical formula C₁₉H₁₅NO₈. By means of spectral analysis of UV, IR, NMR and MS, its structure was identified as phenanthrene compound, 3,4-methylenedioxy-6,8-dimethoxy-10-nitro-1-methyl ester phenanthrene (6-methoxy aristolochic acid methyl ester). It was found for the first time in this plants.