A series of experimental methods including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bro-mide (MTT) test,alkaline phosphatase (ALP) activity measurement,mineralized function,Oil Red O stain and measurement were employed to assess the effect of Dy3+ on the osteogenic and adipogenic differentiation of mouse primary bone marrow stromal cells (BMSCs) and the adipogenic trans-differ-entiation of mouse primary osteoblasts (OBs). The results showed that Dy3+ had no effect on BMSC proliferation at concentrations of 1×10-8 and 1×10-5 mol/L,but inhibited BMSC proliferation at other concentrations. Dy3+ had no effect on OB proliferation at concentrations of 1×10-10 and 1×10-9 mol/L,but inhibited OB proliferation at other concentrations. Dy3+ had no effect on the osteogenic differentia-tion of BMSCs at concentrations of 1×10-9 and 1×10-7 mol/L,and promoted osteogenic differentiation of BMSCs at other concentrations at the 7th day. The osteogenic differentiation of BMSCs was inhibited by Dy3+ at concentration of 1×10-5 mol/L at the 14th day,but promoted osteogenic differentiation of BMSCs at concentrations of 1×10-9,1×10-8,1×10-7 and 1×10-6 mol/L with the maximal effect at concen-tration of 10-6 mol/L. Dy3+ promoted mineralized function of BMSCs at any concentration. Dy3+ had no effect on adipogenic differentiation of BMSCs at concentration of 1×10-7 mol/L,but inhibited adipogenic differentiation of BMSCs at other concentrations. Dy3+ inhibited adipocytic trans-differentiation of OBs at any concentration,suggesting that Dy3+ had protective effect on bone and the protective effect on bone may be mediated by modulating differentiation of BMSCs away from the adipocyte and inhibiting adipocytic trans-differentiation of OBs which may promote differentiation and mineralization of OBs. These results may be valuable for better understanding the mechanism of the effect of Dy3+ on pathogenesis of osteoporosis. A series of experimental methods including 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyl tetrazolium bro-mide (MTT) test, alkaline phosphatase (ALP) activity measurement, measurement were employed to assess the effect of Dy3 + on the osteogenic and adipogenic differentiation of mouse primary bone marrow stromal cells (BMSCs) and the adipogenic trans-differ- entiation of mouse primary osteoblasts (OBs). The results showed that Dy3 + had no effect on BMSC proliferation at concentrations of 1 × 10-8 and 1 × 10-5 mol / L, but inhibited BMSC proliferation at other concentrations. Dy3 + had no effect on OB proliferation at concentrations of 1 × 10-10 and 1 × 10-9 mol / L, but inhibited OB proliferation at other concentrations. Dy3 + had no effect on the osteogenic differentiation-BMSCs at concentrations of 1 × 10-9 and 1 × 10-7 mol / L, and promoted osteogenic differentiation of BMSCs at other concentrations at the 7th day. The osteogenic differentiation of BMSCs was inhib ited by Dy3 + at concentration of 1 × 10 -5 mol / L at the 14th day, but promoted osteogenic differentiation of BMSCs at concentrations of 1 × 10 -9, 1 × 10 -8, 1 × 10 -7 and 1 × 10- Dy3 + had no effect on adipogenic differentiation of BMSCs at concentration of 1 × 10-7 mol / L , but inhibited adipogenic differentiation of BMSCs at other concentrations. suggesting that Dy3 + had protective effect on bone and the protective effect on bone may be mediated by modulating differentiation of BMSCs away from the adipocyte and inhibiting adipocytic trans-differentiation of OBs which may promote differentiation and mineralization of OBs. These results may be valuable for better understanding the mechanism of the effect of Dy3 + on pathogenesis of osteoporosis.