Objective To investigate the expression of stromal cell-derived factor-1 (SDF-1) and its clinical significance in blood plasma of patients with breast tumor. Methods The level of SDF-1 protein was examined by enzyme linked immunosorbent assay (ELISA) in blood plasma of 26 patients with breast benign tumor and 52 patients with breast cancer. Results The SDF-1 protein in blood plasma was detected in both breast benign tumor patients and breast cancer ones. The level of SDF-1 protein in patients with breast cancer was higher than that in ones with breast benign tumor, and there was a statistical difference between them （P=0.000）. In patients with breast cancer, the level of SDF-1 protein in axillary lymph node (ALN) metastasis positive patients was significantly higher than that in ALN metastasis negative ones （P=0.036）. Conclusion The level of SDF-1 protein in blood plasma may be a specific tumor marker. Its level is correlated with lymph node involvement in breast cancer.