Abstract: Objective 　To study the changes and function of plasma CXCL12 levels in patient s with breast cancer. Methods 　Enzyme-linked immunosorbent assay( ELISA) was available to detect the plasma CXCL12 levels in 54 patient s with breast cancer, 20 patients with benign breast tumors and 18 normal healthy donors, analysis the correlation of plasma CXCL12 and the clinical pathological parameters of breast cancer, the changes of plasma CXCL12 by clinical treatment s. Results 　Plasma CXCL12 levels in reast cancer group were significantly higher than those of the two cont rol groups, patient s of stage Ⅲ and Ⅳ, axilla lymph nodes positive and distant metastasis were significantly higher than those of stage Ⅰand Ⅱ, lymph nodes negative and non-distant metastasis, the levels of plasma CXCL12 were remarkably reduced after effectual treatments ( P < 0. 05), no significant correlation was found between plasma CXCL12 and the other clinical pathological parameters of breast cancer, plasma CXCL12 levels of the two ontrol groups showed no significant difference ( P > 0. 05) . Conclusion 　Chemokine CXCL12 play an important role in breast cancer metastasis, it may serve as a novel tumor marker for breast cancer.