Abstract: Objective To investigate the significance of serum matrix metalloproteinase-9（MMP-9） in predicting efficacy of neoadjuvant chemotherapy（NCT） for locally advanced breast cancer. Methods Eighty breast cancer patients of stage Ⅱ-Ⅲ from July 2012 to June 2013 were enrolled in this study. Sixty-four patients with positive expression of ER and PR received EC-T regimen（epirubicin 90mg/m2 iv d1, cyclophosphamide 600mg/m2 iv d1,21 days was a cycle for 4 cycles; and then docetaxel 80mg/m2 iv d1, 21 days was a cycle for 4 cycles）, and 16 patients with negative expression of ER and PR were applied with TEC regimen（docetaxel 75mg/m2 iv d1, epirubicin 7585mg/m2 iv d1, cyclophosphamide 600mg/m2 iv d1,21 days was a cycle for 4 cycles）. The relationship between clinical efficacy of NCT，clinicopathological features and serum MMP-9 levels was analyzed. Results Eighty patients received NCT of 290 cycles. The response rate（RR） was 78.8％（63／80）with 4 cases of CR and 59 cases of PR. The RR of serum MMP-9 positive（＞900U／L）and MMP-9 negative（≤900U／L） in patients with breast cancer before NCT were 85.2％（46／54） and 654％（17／26）with significant difference（P＜0.05）. The serum MMP-9 level was related to stages before NCT, the expression of HER2, ER and PR condition, and pathological reactivity（P＜0.05）. The serum MMP-9 levels after 2 cycles of NCT in patients with effective results, stage Ⅲ（before NCT）, HER-2+, ER+, PR-/+, different pathological reactivity and menopause condition were significantly lower than those before NCT（P＜0.05）. Conclusion The serum MMP-9 level is of predictive value towards NCT for breast cancer，facilitating the development of effective treatment programs.