Objective：To investigate the effects of survivin siRNA on angiogenesis of human breast cancer MCF-7 cell xenografts in nude mice. Methods：The animal model of tumor xenograft was established by transplantation with MCF-7 cells into nude mice. The models were randomly assigned to 3 groups: PcDNA3-Survivin siRNA treatment, PcDNA treatment and control group, which were respectively injected with PcDNA3-siRNA plasmid, PcDNA3 empty plasmid or saline solution into the xenograft tumor after tumor formation in the mice. Survivin mRNA and protein levels were examined by RT-PCR and Western blot. Microvessel density was measured by immunohistochemistry staining. Results：Survivin mRNA, protein levels and microvessel density in PcDNA3-Survivin siRNA treatment group were significantly decreased compared with PcDNA treatment and control group (P﹤0.05)； whereas no significant difference was noted between PcDNA treatment and control group (P﹥0.05). Conclusions：Survivin siRNA not only decreases survivin expression, but also inhibits angiogenesis in MCF-7 xenografts.