This is a multi-center , open-lable clinical trial. Triple-negative breast cancer (TNBC) is a term applied to breast cancer cases that have <1% expression of the estrogen receptor (ER) and the progesterone receptor (PR) and do not over express HER2. TNBC is diagnosed in 15-20% of breast cancer cases and tends to occur in younger women and have biologically more aggressive high grade disease. The purpose of this study is to assess the efficacy and safety of the following two combinations: i) nab-paclitaxel+carboplatin； ii) nab-paclitaxel+capecitabine in subjects with advanced TNBC and up to one prior line of systemic treatment for metastatic disease. Maintenance therapy with capecitabine after completion of combination chemotherapy.