Abstract: Objective :To explore the putative effects of neo-adjuvant CAF regimen chemotherapy on the expression of BCSG1 in breast cancer. Methods :The expression of BCSG1 of cancer cells was studied with immunohistochemical staining in 34 cases of breast cancer with and 110 cases without preoperative necadjuvant CAF regimen chemotherapy in same period. The therapeutic:response of neo-adjuvant chemotherapy was evaluated with pathological observation. The relationship between expression of BCSG1 and pathological response to the chemotherapy was analyzed. Results : The overall response rate of the neadjuvant chemotherapy was 79.4% and the strong expression of BCSG1 was significantly lower than the controls (29.4% vs 64.5%, P<0.01). In chemotherapy group, the positive expression in PR (II degree) cases was significantly lower than those in NR (III degree) cases (P=0.002). Conclusions : The neo-adjuvant chemotherapy with CAF regiment could decrease the expression of BCSG 1 in breast cancer.