Objective:To investigate the side population cells in Huh7 and their different proliferation and division ability,which may play a key role in the treatment of hepatocellular carcinoma. Methods:Huh7 cells were sorted by fluorescence-activated cell sorter (FACS),and the hoechst33342 fluorescence intensity of side population and main population cells is measured under fluorescence microscope. ABCG2 mRNA levels in side population and main population cells were examined by RT-PCR,which was checked by sequencing. The expression of ABCG2 protein in the clones formed by side population and main population cells was measured by fluorescence immunoassay,and the cell number in ABCG2(+)or ABCG2(-)clones was counted under fluorescence microscope. Results:In the absence of verapamil,the ratio of side population cells was 2.22%,while in the presence of verapamil the ratio decreasesd to 0.74%. Side population cells looked dimmer than main population cells under fluorescence microscope. ABCG2 mRNA level in side population cells was 4.32 times of that in main population cells (P < 0.01). The proliferation ability of side population cells was 2.7 times of that in main population cells (P < 0.01). What’s more,side population cells can differentiate into ABCG2(+)and ABCG2(-)offspring,while main population cells can only differentiate in to ABCG2(-)offspring. Conclusion:Side population cells do exist in Huh7 cell line,and they have stronger proliferation ability compared with main population cells,and asymmetric cell division ability(self-renewal and directed differentiation),which is a key character of stem cells. The isolation of side population cell can be a useful method to isolate cancer stem cell,and these side population cells may play a key role in drug resistance and tumor progression of hepatocellular carcinoma. Further study of the biological behavior of side population cells may pave a new way to the treatment of hepatocellular carcinoma.