This is a single-center phase Ⅱ study designed to evaluated the efficacy and safety of pegylated liposomal doxorubicin（PLD）in combination with trastuzumab in HER-2 positive metastatic breast cancer .

Inclusion Criteria:

• Ability to understand and voluntarily receive the research procedures according to protocol,willingness to sign the written informed consent document;
• Female patients aged from 18 to 70 years old；
• Histologically confirmed as invasive breast cancer；
• HER-2 Positive（defined by: IHC 3+ or ISH positive）, regardless of HR status;
• Recurrence after adjuvant therapy or metastatic breast cancer，and chemotherapy naïve in the metastatic setting or had one prior regimen for metastatic breast cancer；
• Patients must have measurable disease according to RECIST criteria Version 1.1（Brain metastases lesions and bone metastases lesions were excluded）;
• The adverse event caused by prior therapy has recovered, or stabilized, or does not affect the study administration according to the investigator's judgment；
• Performance status 0-1；
• Life expectancy of at least 3 months；
• Left ventricular ejection fraction (LVEF)≥55%；
• Brain natriuretic peptide (BNP) and cardiac troponin T (cTnT) were in the normal range；
• Patients must have normal ECG；
• Bone marrow function: absolute neutrophil count (ANC)≥1.5×109/L，platelets≥100×109/L，hemoglobin ≥90g/L；
• Hepatic function：alanine aminotransferase(ALT) and aspartate aminotransferase(AST) ≤2.5×ULN，serum total bilirubin≤ 1.5×ULN，or ≤2.5×ULN who has Gilbert's syndrome;
• Renal function：serum creatinine≤1.5×ULN；
• Coagulation function：the international standardized ratio (INR) ≤1.5×ULN, prothrombin time (PT) or the activated partial thrombin time (APTT) ≤1.5×ULN.

Exclusion Criteria:

• Patients with symptomatic brain metastases.
• Patients who are known or suspected to be allergic to the active ingredient or excipients of the investigational drug.
• Prior cumulative dose of 240 mg/m2 for doxorubicin and 400 mg/m2 for epirubicin.
• Prior treatment with anthracyclines has caused cardiotoxicity, or failed (disease progression during therapy or recurrence and metastasis within 12 months after adjuvant therapy).
• Prior mediastinal radiotherapy.
• Participation in other clinical trials within 4 weeks before enrollment.
• Severe cardiovascular disease, including history of congestive heart failure, acute myocardial infarction within 6 months before enrollment, transmural myocardial infarction measured by ECG, uncontrolled arrhythmia, angina requiring therapy, clinically significant valvular heart disease, uncontrolled hypertension.
• Severe or uncontrolled infection.
• Positivity for HIV, Hepatitis B or C.
• Active malignancy in the past 5 years (other than carcinoma in situ of the cervix or basal cell carcinoma of the skin).
• Patients who are pregnant , breastfeeding ,or refuse to use adequate contraception during the course of participation.
• Need to concurrent other cancer therapy(other than palliative care for non-target lesions).
• Other ineligible conditions according to the researcher's judgment.