Objective To investigate the expression of claudin-1 in breast tumor tissues and the relationship of development and progress of breast neoplasm．Methods The expressions of claudin-1 in 89 cases of breast cancer and 37 benign breast diseases were tested by tissue chip technology and immunohistochemistry．The relationships of claudin-1 expression to the lymph node metastasis，TNM staging，maximum diameter of the tumor，and histology grade were statistically analyzed．Results The expression of claudin-1 in the breast cancer was significantly lower than that in the benign breast disease（χ2=19.20，P=0.000 2）．The claudin-1 expression in the patients with lymph node metastasis was significantly lower than that without lymph node metastasis （χ2=3.85，P=0.049 7）．The claudin-1 expression in the stageⅢ of TNM staging was weaker than that in the stage Ⅰ（χ2=5.29，P=0.021 4） and stage Ⅱ （χ2=7.46，P=0.006 3），respectively. There was no significant difference of the claudin-1 expression in the different maximum diameters of tumor （χ2=1.58，P=0.453 8） or histology grades （χ2=1.02，P=0.600 5），respectively．Conclusions The expression of claudin-1 might be correlated with the occurrence，development，and metastasis in breast tumor．It may be one of the potential indicator for lymph node metastasis and prognosis assessment in breast cancer．