Abstract: Objective To compare morphology，proliferation capacity and purity of human marrow mesenchymal stem cells by two isolation methods in vitro. Methods Human marrow mesenchymal stem cells were isolated by whole marrow culture and density gradient centrifugation. The appearance of the cells and growth curves of the third generation cells were observed. 1×105 of the third generation cells were cultured and counted continuously for 30 days. Surface antigens of the stem cells were detected with flow cytometry. Results The cells isolated by the two methods were both like long shuttle；the primary passage time of cells by whole marrow culture was 10d and the double time was 30±5.6h，while the primary passage time by density gradient centrifugation was 18d and double time was 38±7.2h；The total numbers of the former were 15 times more than the latter at 30th day. FACS showed that positive rates of CD73，CD105 and CD166 in the third generation cells isolated by whole marrow culture were less than that by density gradient centrifugation（P<0.05）. Conclusion The two methods we used can successfully isolate human marrow mesenchymal stem cells. The former has a stronger proliferation ability and the latter has a higher purity of the stem cells.

Key words: Mesenchymal stem cells, Bone marrow, Cell surface