To study the chemical constituents of Oldenlandia diffusa.The chemical constituents were isolated and purified by silica gel and Sephadex LH-20 column chromatography as well as recrystallization method, and their structures were elucidated on the basis of physical and spectral analyses.Nine compounds were isolated and their structures were identified as quercetin (1), kaempferol (2), scopoletin (3), 2-hydroxy-3-methylanthraquinone (4), 2-hydroxy-l-methoxyanthraquinone (5), α-linolenic acid (6), vanillic acid (7), p-hydroxyphenylethanol (8) and, β-sitosterol (9).Compound 6 is obtained from this genus for the first time. Compounds 7 and 8 are obtained from this plant for the first time.