Triple-negative breast cancer (TNBC) is defined as the absence of estrogen and progesterone receptor expression as well as ERBB2 amplification. It has no response to endocrine or anti-ERBB2 therapies. Recent studies have found some potential therapeutic targets for TNBC. However, it still has a poor outcome. It was reported that TNBC has six subtypes, including 2 basal-like (BL1 and BL2), an immunomodulatory (IM), a mesenchymal (M), a mesenchymal stem-like (MSL), and a luminal androgen receptor (LAR) subtype. Different subtype may be sensitive to different treatment. Bicalutamide is an oral, non-steroidal, androgen receptor (AR) antagonist. It is approved by the Food and Drug Administration (FDA) for the treatment of metastatic prostate cancer. Recently, a study explored the efficacy of bicalutamide in AR positive, estrogen receptor negative metastatic breast cancer (MBC), which showed a high clinical benefit rate (CBR) and a good safety profile. Based on the above reasons, we initiate this phase II study to evaluate the efficacy and safety of bicalutamide in AR positive metastatic triple-negative breast cancer patients.