A Randomized, Open-label, Multi-center Phase III Study Comparing the Efficacy of Oral Chemotherapy Combined With Trastuzumab Versus Paclitaxel Combined With Trastuzumab in the Adjuvant Treatment of HER2-positive, Lymph Node-negative Early Breast Cancer Patients(ORCHID-PLUS)

Inclusion Criteria: 1. Females aged 18\~70; 2. The postoperative pathological stage of early breast cancer is stage IA: the longest diameter of invasive cancer is not more than 2cm and the lymph node is negative: pT1mic-T1cN0M0 (micro-invasion needs to meet multiple foci). 3. Pathological immunohistochemistry must meet the following conditions: HER-2 (3) or HER-2 (0-2) but amplified by FISH or CISH testing. 4. The maximum number of weeks (56 days) from surgery to randomization is not more than 8 weeks (56 days). 5. The function of major organs is normal, that is, the following criteria are met: (1) The criteria for routine blood examination must meet: HB ≥90 g/L (no blood transfusion within 14 days); ANC ≥1.5×109 /L； PLT ≥100×109 /L； (2) Biochemical tests must meet the following standards: TBIL ≤1.5×ULN (upper limit of normal value); ALT and AST ≤3×ULN; Serum Cr ≤1×ULN, endogenous creatinine clearance \>50 ml/min (Cockcroft-Gault formula); 6. Cardiac function: ECG was generally normal, QTc \< 470 ms, LVEF \>50%; 7. The subjects voluntarily joined the study, signed the informed consent form, had good compliance, and cooperated with the follow-up Exclusion Criteria: 1. Patients who have received neoadjuvant therapy, including chemotherapy, targeted, radiotherapy, or endocrine therapy; 2. History of other malignant tumors in the past, except for cured basal cell carcinoma of the skin and carcinoma in situ of the cervix; 3. metastasis of any site; 4. Pregnant or lactating women, women of childbearing age who cannot use effective contraception; 5. Patients who are also participating in other clinical trials; 6. Severe organ function (heart, lung, liver, kidney) insufficiency, LEVF \< 50% (ultrasound), severe cardiovascular and cerebrovascular diseases (such as: unstable angina, chronic heart failure, uncontrolled hypertension \>150/90mmgh, myocardial infarction or cerebrovascular accident) within 6 months before enrollment; Diabetic patients with poor glycemic control; Patients with severe hypertension; 7. Severe or uncontrolled infection; 8. Those who have a history of psychotropic drug abuse and cannot be quit or have a history of mental disorder; 9. Patients who are judged by the investigator to be unsuitable to participate in this study.