Abstract: Poly ( ADP-ribose ) polymerase-1 ( PARP-1 ) has a vital role in base excision repair of single-strand DNA breakage, and its over-expression has often been observed in various human tumor types, which correlates with a poor outcome. PARP-1 inhibition has been exploited in the repair of double-strange DNA breakage through a synthetic lethal approach for killing tumor cells with defects. This process is done via homologous recombination, particularly in the context of BRCA1 or BRCA2 mutation. Many clinical trials have demonstrated the clinical application value of PARP inhibitors in the treatment of cancer with BRCA mutations. PARP-1 will be an important target of tumor therapy.