Objective: The aim of this study was to study changes of HER-2 expression after neoadjuvant chemotherapy in the breast cancer cases. Methods: One hundred and thirty-seven female patients with primary breast cancers, who received neoadjuvant chemotherapy, underwent core needle puncture and Mammotome biopsy before chemotherapy, and the biopsy results were used as the basis of histological diagnosis, fluorescence in situ hybridization (FISH) was performed to test HER 2 status of tumor tissues before and after chemotherapy. All patients underwent FEC, TE, or AC neoadjuvant chemotherapy of 2-6 cycles before surgery. Results: Twenty-two patients were positive according to FISH test among 137 preoperative patients, 8 patients achieved pathological complete remission after chemotherapy (three HER-2 positive patients and five negative patients), 91 patients achieved partial remission, 24 patients were stable, and 14 cases were invalid. Twenty-two patients were positive according to FISH test (8 patients with pathological complete remission did not undergo test), and positive patients still expressed positively after chemotherapy before neoadjuvant chemotherapy. Three negative patients were converted to be positive, and changes before and after chemotherapy had no statistical difference (P > 0.05). Conclusion: Neoadjuvant chemotherapy makes no influence on patients with HER-2 positive expression, while patients with negative expression can be converted to be positive, but without significant difference.