Abstract: Objective: To study the relationship between the expression of occludin and malignancy multiplication in different human breast cancer cell lines MCF-7,MDA-MB-231 and SKBR-3. Methods: Cell proliferation was determined by MTT assay. The cell cycle was measured by flow cytometry. The adherence was detected by fibronectin protein. The migration of cells was detected by Transwell. The expression of occludin mRNA was examined by semi-quantitative RT-PCR. Western-blot and immunohistochemistry were used to detected the protein expression of occludin. Results: Human breast cancer cell lines MCF-7 cell malignant proliferation. S phese was less than the propotion of human breast cancer cell lines MDA-M B-231 and SKBR-3 (P < 0.05-P < 0.01). The expressions of occludin mRNA and protein in the human breast cancer cell line MCF-7 were higher than that of human breast cancer cell lines MDAMB-231 and SKBR-3(P < 0.01),and the migration and adherence was weaker than that of human breast cancer cell lines MDA-MB-231 and SKBR-3(P < 0.01). Conclusions: The expression of occludin is negatively related with human breast cancer cells malignant proliferation growth,adherence and migration.