It was well recognized that mechanical strain plays a crucial role in periodontal tissues remodeling. The aim of this study was to investigate the effect of mechanical strain on osteoblastic precursor cells in a collagen type I gel scaffold. Rat MSCs were isolated and cultured according to the established method. Cells were induced with osteogenic medium, then seeded in a collagen type I gel and mechanically stretched by application of cyclic biaxial strain 24h later. Strain cycle was set to 1 cycle/min (0.017Hz), and strain magnitude was set to 2%, 5%, 7% elongation. Cells were collected in 0h, 3h, 6h, 9h, 12h, 24h and 48h respectively. ODF and ICAM-1 mRNA were analyzed by RT-PCR assay. The results shown that 2-7% elongation strain, either dynamic or static, inhibited ICAM-1and ODF expression of osteoblastic precursors, and the effects were relative tightly to strain magnitude. The inhibition effects of dynamic strain loading group exceeded the corresponding static strain. This work suggested that appropriate mechanical strech may suppress differentiation of osteoclasts through inhibiting expression of ICAM-1 and ODF. Application of mechanical stress might have a beneficial effect on quantity of generated bone tissue and might be a important factor in tissue engineering of periodontal tissues.