Abstract: Tumor is one of the important causes that threaten human survival and health. Chemotherapy is one of the commonly used methods in tumor therapy, but its application is limited by its low specificity, serious adverse drug reaction, and it is also easy to produce drug resistance after long-term use. Novel anti-tumor drug poly-ADP ribose polymerase(PARP) inhibitors based on DNA damage repair mechanisms may be the key to solve this problem. PARP inhibitors are a new class of anti-tumor drugs targeting inhibition of PARP-1 protein and induce “synthetic lethal” phenomenon in tumor cells with BRCA gene mutations. It has been successfully used in the treatment of ovarian cancer, breast cancer and other tumors. In recent years, it has expanded the scope of clinical application through combining with various first-line chemotherapy drugs, targeted drugs and immuno checkpoint inhibitor. In this paper, the pharmacological action and mechanism of PARP inhibitors, the application of PARP inhibitors in tumor therapy and the mechanism of drug resistance of PARP inhibitors will be summarized to provide reasonable guidance for its clinical application.