Abstract: Objective To investigate the correlation amony BMP9 expression, migration and invasion of breast cancer MDA-MB-231 cells in vitro. Methods The expression of BMP9 in MDA-MB-231 was detected by RT- PCR, high titer of adenovirus vector expressing BMP9 was used to infect MDA-MB-231.Experimental group: MDA-MB-231/BMP9，control group: MDA-MB-231/GFP and MDA-MB-231.To detect the changes of invasion and migration in the recombinant MDA-MB-231/BMP9 cells colony-forming assay, cell wounding assay, Transwell invasion assay were carried out. Results Compared with MDA-MB-231/GFP cells and MDA-MB-231 cells, the mRNA level of BMP9 was increased in MDA-MB-231/BMP9 cells. the cell colony formation rate of experimental group was decreased from the control group (95.4 ± 3.1)% and (92.5 ± 2.4)% to (74.0 ± 3.6)% (P <0.05), the healing rate of experimental group was decreased from control group (95.4 ± 3.1)% and (92.5 ± 2.4)% to (74.0 ± 3.6)% (P <0.05) , the number of invading cells which moved across the matrix barrier for experimental group was decreased from control group (255.3±16.1) and (267.3±14.9) to（150.3±14.6）(P<0．05). Conclusion BMP9 can inhibit the invasion, and migration of breast cancer in vitro.