Abstract： Objective To study cytotoxic and antineoplastic effect in vitro of tephroseris kirilowii turez, houlub extract on U266 multiple myeloma cell line. Methods U266 cells were cocultured with the tephroseris kirilowii turez, houlub extract. Cytotoxicity assay was used by CCK-8 detection kit. Cell cycle and apoptosis were determined using flow cytometry(FCM) analysis. Results Extract of tephroseris kirilowii turez, houlub showed strong cytotoxicity against U266 cells.The IC50 was about 3.2 mg/L. After exposure of U266 cells to the drug, the distribution of cell cycle was changed compared with that of the controls. When the durg concentration was 1.25, 2.5, 5 and 10 mg/L. respectively, the pencentages of cells in the G0/G1 phase were decreased with (34.12±0.49) %, (38.06 ± 0.63) % , (27.46±0.61) %, (15.91±0.32) %, respectively, while those in the S phase were increased with (4.98± 0.50) %, (4.01±0.22) %, (4.16±0.15) % and (5.04±0.12) % in G2/ M phase were increased with (50.05 ±1.12) %, (51.27±0.71) %, (51.84±0.73) % and (55.11±0.25) %, respectively, and apoptosis cells were increased. Apoptosis of U266 cells inadose-depadeut manner could be deteted with staining of Annexix V FITC/PI testing through FCM. Conclusion Tephroseris kirilowii turez extract showed strong cytotoxic effect on U266 cells. The antineoplsastic mechanism of the drug can be partly due to its induced apoptotic effect.