Objective: To research the expression of PTEN and its influence on biological ability in breast cancer cell in vivo. Methods: PTEN-shRNA plasmid was transtected into M231 breast cancer cells to knock down the expression of PTEN. The changes of PTEN expression, proliferation, adhesion and metastasis of PTEN knocked down cell were tested by western-blot, colony formation, adhesion and invasion assay. Results: PTEN-shRNA was successfully transfected into M231 cells and it inhibited PTEN expression efficiently.The capabilities of colony formation, migration and invasion of transfected cell were much greater than those of the controlling cell line. But the transfected cells were more difficulty in adhesion than the scrambled ones. Conclusion: PTEN genecan enhance the adhesion, but restrict the proliferation, migration of breast cancer cells in some degree, so that inhibit the development of the breast cancer. PTEN loss can be a prognostic factors for the patients with breast cancer.