Objective This study explored the effects of the effective component of Chinese herbs on the morphology,ultrastructure and terminal differentiation phenotype of human osteosarcoma,and in addition identified its inducing function of terminal differentiation of MG-63 cell. Methods MG-63 cells were treated with the combination of 33 mg/L ginsenoside Rg1,2mmol/L cinnamic acid and 0.3 mg/L tanshinoneIIA(RCT) for 7 days and three samples of each groups were subjected to immuncocytochemical assay,and light and electromicroscopy. The MG-63 cells treated by hexamethylene bisacetamide(HMBA) were investigated as a positive control of induced differentiation. Results Immunocytochemistry analysis revealed that the expression of the molecular biomarkers of terminal differentiation,including type Ⅰ collagen，osteocalcin and osteonectin,were notabley positive,and more calcified glycogen particles and classic bone nodules were obsreved in the RCT treated cells.Using light and electromicroscopy, we found that the morphology and ultrastructure of MG-63 cells had undergone restorational changes after RCT treatments similar to that of normal cells: the cells were regular and inclined to have the same size, the size increased, the nucleo-cytoplasm ratio lessened, the number and size of nucleous decreased, organelles tended to be well-developed, and were typical and polarized. Conclusion From these observations we have drawn the conclusion that RCT could reverse the malignant phenotypes of tumor cells, promote the expression of terminal differentiational biomarkers, and remarkably induced MG-63