Objective:To investigate effects of microRNA-145 (miRNA-145) on growth and angiogenesis of osteosarcoma in vivo. Methods: Sixteen nude mice (Balb/c)were randomly divided into 2 groups,experimental group and control group,with 8 mice in each group. The animal model of experimental group was constructed by subcutaneous inoculation of osteosarcoma cells transfected with miRNA-145,and control group using subcutaneous inoculation of osteosarcoma cells. The osteosarcoma-bearing nude mice were feeded for 4 weeks. After 4 weeks,tumor formation rate,size,and weight of tumor were observed in each group. Ⅷ factor expression and VEGF expression of tumor were detected by immunohistochemistry and microvessel density were calculated. Results: The tumor formation rate is 87.5% and 37.5% in control group and experimental group respectively. The size and weight of tumor in experimental group is significantly less than that of the control group (P < 0.05). The VEGF expression and MVD of tumor in the experimental group is significantly lower than those in that of the control group (P < 0.05). Conclusion: miRNA-145 can inhibit osteosarcoma formation of nude mice,and inhibit growth and angiopoiesis of tumor in vivo.