Inclusion Criteria:  Age between 18 and 75 year-old women； ECOG score: 0-1； HER2 positive breast cancer diagnosed histologically is defined as HER2 (3+) by immunohistochemistry or HER2 (2+) with positive FISH test； Postoperative pathological stage ⅱ → ⅲ, or initial stage (before neoadjuvant therapy) ⅱ → ⅲ, radiographic assessment showed no metastasis; Complete 1 year of anti-HER2 therapy with trastuzumab, prior use of pertuzumab neoadjuvant + adjuvant therapy or T-DM1 adjuvant therapy is permitted; No major organ dysfunction, contraception; The patients have good compliance to the therapy and follow-up to be scheduled and are able to understand the study protocol and sign the Informed Consent Form.  Exclusion Criteria:  Patients who are allergic to the study drug, cannot take the drug orally, or refuse the medication regimen; Prior treatment with TKI anti-HER-2 drugs (e.g. Lapatinib, Pyrotinib, etc.); Patients were enrolled in other studies or stopped taking other drugs within 4 weeks; Patients with serious dysfunction of important organs (heart, liver and kidney); Patients with other malignancies, other than cured non-melanoma skin cancer, carcinoma in situ of the cervix and other tumors that have been cured for at least 5 years; In pregnancy, lactation patients; In the active stage of other acute or chronic infectious diseases; The patients have uncontrollable mental illness; There is a known history of human immunodeficiency virus; There are other circumstances in which the investigator suggested that the patient should not participate in the study.