Abstract: Objective :To evaluate the effects of Matrine on the proliferation and apoptosis of human oral epidermoid carcinoma KB cells and it's moutidrug resistant counterpart IBv200 Cells. Methods :The proliferation and apoptosis of KB Cells and KBv200 were studied comparatively after matrine treatment with the following methods. MTT assay was used to evaluate the inhibition ability of matrine on the cells in vitro. Transmission electron microscope was used to observe the ultrastructure feature of cells after treated by matrine. Acridine orange (AO)/ethidium bromide (EB) fluorescent staining and flow cytometry were used to observe apoptosis induced by matrine. Flow cytometry was applied to study the effects of the drug on cell cycles as well as apoptosis of the two cells. Results :The vital rates of both KB and KBv200 cells in vitro were decreased after matrine treatment at different concentrations(0.50、1.00、1.50,2.00 mg/ml). The ICSO concentrations of matrine on KB and KBv200 cells are 1.35 ml and 1.43 mg/ml respectively, no sognificant difference was found between the two cells. The results of AO/EB fluorescent staining and flow cytometry showed that matrine could induce apoptosis of two cells. Under transmission electron microscope, condensation of nuclei, bubble of cytoplasm could be seen in both cell line in matrine treated cells. Matrine could block the growth of KB and KBv200 cellsat S phase. Conclusions :Matrine could inhibit the proliferation and induce apoptosis of lx>th KB and it's moutidrug resistant counterpart KBv200 cells. No differences were found in these effects between the two cells,suggesting that matrine could overcome multidrug resistance in the treatment of cancer and mayof wider usage in ontological practice.