• Adult female patients with advanced breast cancer diagnosed by pathology (aged 18-75, including 18 and 75 years old), not suitable for surgical resection or radiation therapy for the purpose of cure;

• Pathological examination confirmed ER and / or PR positive, HER-2 negative (Positive ER expression: immunohistochemistry \>1% tumor cell staining; Positive PR expression: immunohistochemistry \>1% tumor cell staining; HER-2 negative: immunohistochemistry is 0,1+, or FISH/CISH negative when immunohistochemistry is 2+);

• Patients with advanced breast cancer who have no disease progression after a 4-8-course first-line chemotherapy regimen (the effect is evaluated as complete response/ partial response/ stable disease). Capecitabine monotherapy as first-line chemotherapy is allowed and the courses of treatment should be limited to 6.

• WHO physical status 0-1 points, estimated lifetime at least 3 months;

• Imaging examinations within 3 weeks before enrollment were required for assessing tumor lesions before maintenance treatment (Examination results from local Tertiary A hospital are available);

• Previous treatment-related toxicity should be relieved to ≤ Grade 1 according to NCI CTCAE (version 4.03) before randomization (Except for hair loss and other toxicities that are not at risk to the patient's safety based on the investigator's judgment);

• The routine blood test was normal within 1 week before enrollment: WBC ≥3.0×10\^9／L, b. ANC ≥1.5×10\^9／L, c. PLT ≥100×10\^9／L;

• The liver and kidney function test was normal within 1 week before enrollment (Take the normal value of the laboratory of each research center as the standard): a. TBIL≤1.5× Upper Limit of Normal (ULN)b. ALT/AST≤2.5×ULN（Liver metastasis patients ≤5xULN） c. Serum Cr ≤1.5×ULN, or Ccr ≥60 ml/min;

• Informed consent form signed before enrollment.