Abstract: Objective To explore the expression of P-gp and GST-π in breast cancer tissue receiving neoadjuvant chemotherapy and explore its clinical significance. Methods Expressions of P-gp; GST-π in 100 breast cancer patients before and after neoadjuvant chemotherapy were measured by immunohistochemistry Envision method. The relationship between P-gp, GST-π and the effect of neoadjuvant chemotherapy was analyzed by chi-square test. Results The overall response rate to neoadjuvant chemotherapy was 79%. In patients with P-gp, GST-π positive expression, the response rate to chemotherapy were 69.04%, and 77.08%, and in patients with P-gp, GST-π negative expression, the response rate to chemotherapy were 86.20%(P<0.05) and 80.76%(P>0.05). The positive expression of P-gp before and after chemotherapy were 41.75% and 64.83%, respectively, and their difference was statistically significant (P<0.05). The positive expression of GST-π before and after chemotherapy were 49.45% and 54.94%, respectively, and no difference was found between them(P>0.05). Conclusion The expression of P-gp increased significantly after neoadjuvant chemotherapy. It suggested that P-gp could be used to predict the therapeutic efficacy of neoadjuvant chemotherapy.