BRCA1 is a 220kDa nuclear protein with multiple functional domains. It interacts directly or indirectly with a variety of important proteins, including oncogene proteins (c-myc, E2F), tumor suppressor proteins (p53, RB, BRCA2), DNA damage repair proteins (RAD50, RAD51), cell-cycle regulators (cyclin, CDK), transcriptional regulators (RNA polymerase II) and others related to the important biological events. BRCA1 is likely to play an important role in the maintenance of genomic stability through its activities in cell-cycle progression, DNA damage repair, transcriptional regulation, and apoptosis. Here, the authors provided a review of the biochemistry structure of BRCA1 as well as its role in maintaining the genomic stability.