Abstract: Objective: To study whether Staphylococcus aureus (SA) could invade the cultured human osteoblasts and to investigate whether different infective dose and time affect the number of intracellular bacteria.Methods: Transmission electron microscope (TEM) was used to observe the invasion of SA and the number of cells containing intracellular SA;And the mean fluorescence units of total cells were detected by flow cytometry.Results: TEM showed that SA could penetrate the human ostaoblasts.With the infective dose increasing,the number of intracellular bacteria also grew up,which reached the top at 4 h;The number of intracellular bacteria had no difference at 1 h and 2 h (P>0.05),but the difference was significant at other time points (P<0.01).Conclusions: The results suggest that SA can penetrate the human osteoblasts,and the number of intracellular bacteria is associated with the infective dose and time.