The chemical constituents of Leonurus heterophyllus were separated and purified by repeated column chromatography on silica gel, HPD 100, Sephadex LH-20, and PHPLC. Each compound was characterized by spectroscopic and physical data. Eight compounds have been purified and identified to be Quercetin 3-O-robinobioside (1), rutin (2), isoquerci trin (3), hyperoside (4), quercetin (5), apigenin (6), genkwanin (7), and benzoic acid (8). Among them, compounds 2, 5-7 were isolated from L. heterophyllus for the first time; Compounds 1, 3, 4, 8 were obtained for the first time from the genus Leonurus. The in vitro activities against leukemia K562 Cells of pure components were evaluated by testing their IC50.