Objective To study the effect of serum rich in growth factors (SRGF) derived from plateletrich plasma (PRP) on the biological function of human and rat osteoblast.Methods PRP and platelet-poor plasma (PPP) obtained from healthy human and SD rat were activated by thrombin toget SRGF and serum poor in growth factors (SPGF). The level of TGFβ1 and PDGF-AB in human-SRGF and SPGF were assayed by enzyme-linked immunoassay(ELISA). Rat and human osteoblast were cultured and identified. Rat osteoblasts were treated with 5% rat-SRGF, 5% rat-SPGF and serumfree F12 medium, respectively. And human osteoblast were treated with 5% human-SRGF, 5% human-SPGF and serumfree DMEM. Cellular mitogenic activity was evaluated by thiazoly blue (MTT) colorimetric assay at 24, 48, 72 and 96hours.Results The level of TGF-β1 in human-SRGF was 307.67±35.57 ng/ml, and that of PDGF-AB was 52.76±7.89 ng/ml. The proliferation of rat and human osteoblast were promoted after treated with rat-SRGFand human-SRGF, respectively. In rat osteoblast groups, there were significant differences in absorbency between ratSPGF group and rat-SRGF group at 48 and 96 hours(Plt;0.05). In human osteoblast groups, the differences between human-SPGF group and human-SRGF group were significant at 48, 72 and 96 hours(Plt;0.05). The proliferation of these two kinds of osteoblasts almost stopped in serum-free medium, and the differences in absorbency , compared with othergroups，were significant (Plt;0.05). Conclusion High quality of PRP can be achieved by the improved method and SRGF is capable of up-regulating the proliferation of rat osteoblast and human osteoblast.