Objective:To construct and express a recombinant expression vector containing a mouse parathyroid hormone related protein (PTHrP) 1~84,and to examine the effect of the purified product on bone formation. Methods:The PTHrP1~84 gene fragment was amplified by RT-PCR and inserted into corresponding sites of expression vector pGEX-2TK,and the fusion protein expressed in E.coli BL21 induced by IPTG. After purification and identification,its roles on the proliferation and differentiation of bone marrow mysenchymal stem cells was evaluated in vitro. Results:The new recombinant expression vector pGEX-2TK/mPTHrP1~84 was constructed successfully. The gene recombinant product was soluble. The treatment with purified mPTHrP1~84 in bone marrow cell cultures not only significantly increased colony-forming unit-fibroblast (CFU-f),but also significantly increased alkaline phosphotase and collagen positive CFU-f and calcified nodules. Conclusion:Results demonstrated that gene recombinant mPTHrP1~84 can stimulate bone marrow mysenchymal stem cell to proliferate and differentiate into osteoblasts.