To study the effect of Astragalus polysaccharide (APS) on adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) cultured in hypoxic environment. The optimal APS concentration, which could promote the proliferation of BMSCs, was screened by methyl thiazolyl tetrazolium method. The concentration was used to intervene in BMSCs-induced by adipogenic differentiation fluid growing in different oxygen concentrations (3%, 6%, 10% and 20%). The formation of lipid droplets in the BMSCs-intervened was observed by oil red O staining under the optical microscope. The mRNA and protein levels of the lipid relating genes peroxisome proliferator activated receptor gamma 2 (PPAR-γ2) and lipoprotein lipase (LPL) were detected by Real-time PCR and Western blotting, respectively. The results showed that, comparing with the control group, 40 μg/mL APS could significantly promote the proliferation of BMSCs under low oxygen concentration. A large amount of lipid droplets existed in BMSCs growing in the adipogenic inducing fluid containing 40 μg/mL APS and the hypoxic environment, and the protein and mRNA levels of PPAR-γ2 and LPL also raised. It was worth noting that the phenomenon was more significant in 10% oxygen concentration, and the difference was statistically significant (P<0.05). 40 μg/mL APS had effect on promoting the proliferation and adipogenic differentiation of BMSCs cultured in hypoxic environment, and the effect was related to the concentration of oxygen of BMSCs-cultured.