Objective The proliferation of murine bone marrow stem cells(mBMSCs) is relatively slowly in vitro and gradually lose their phenotype.To study the effect of low oxygen tension on proliferation of mBMSCs in order to find a better way for mBMSCs quick expansion.Methods Murine bone marrow stem cells were isolated and cultured at low oxygen tension(4%O_2) or conventional oxygen tension(20%O_2).Their proliferation,cell morphology and DNA cycle were observed and compared.Results Low oxygen tension(4%O_2) promoted the mBMSCs proliferation,and the cell doubling time(4%O_2) culture was shorter than that of 20%O_2.There were significant cell morphological differences between mBMSCs cultured at 4%O_2 and 20%O_2.Moreover,the portion of cells at 4%O_2 in DNA synthetic period is higher comparing with 20%O_2. Conclusion Low oxygen tension(4%O_2) culture can promote mBMSCs proliferation and it may be a better way to expand mBMSCs in vitro for tissue engineering.