Abstract: Objective To explore if transforming growth factor-β induced gene (TGFBI) could inhibit the proliferation of human breast cancer cell lines MDA-MB-231 in vitro and in vivo. Methods Ectopic TGFBI was stably transfected into MDA-MB-231. Cell proliferation, cell cycle, soft agar cloning efficiency, protein expression of P21 and P53 were analyzed to test tumorigenicity of human breast cancer cells. Results Ectopic TGFBI was expressed highly and stably in MDA-MB-231 cells, with the significant decrease of cells proliferation rate. Compared with V23101 transfected with empty plasmid, ectopic TGFBI expression resulted in a significant decrease of relative soft agar colony formation number by 90.89%. Tumor cells transfected with TGFBI were arrested in the G1 phase and delayed into the S phase. Ectopic TGFBI reduced tumorigenicity by 16.99% and delayed the incubation of tumor growth. Conclusion TGFBI could inhibit the proliferation of human breast cancer cell in vitro and in vivo.