Abstract: Characteristics of the human bone marrow stromal stem cell (hBMSC) growth and differentiation into osteogenic cells in vitro cultures were investigated. It was found that the hBMSCs cultured during the former three passages showed spindle-shaped, rapid growth, and powerful expansion. Gradually, hBMSCs became large flat, grew slowly, and the expansion ability decreased. Up to the sixth passage, the cells lost their proliferation ability. Their growth phase could be divided into three stages: arrearage, logarithm, and stationary. Generally, arrearage stage lasted six to seven days, logarithm stage four to five, then cells came into stability. It was found that the population doubling time (PDT) of hBMSCs at logarithm stage during the former three passages was almost the same, while it increased a little at the fourth and up to the greatest at the fifth passage. Expansion of the hBMSCs in the former three passages reached 18-fold, whereas at the fourth and fifth passages the cell proliferation decreased to 11-fold and 5-fold, (respectively.) Experimental results showed that the hBMSCs cultured in vitro had the ability to form matrix calcification through induction, and the alkaline phosphatase activity was significantly higher than that of the cells not induced.