Abstract: Circular RNA (CircRNA), synthesized through reverse splicing of exons, introns or intergene regions, are characterized by abundant species, conserved sequence, stable structure, tissue specificity, etc. Disordered in many malignant tumors, CircRNA can adjust the repair function of cell DNA double-strand break damage after radiotherapy and chemotherapy, causing a series of adverse reactions such as carcinoma proliferation, distant metastasis and decreased apoptosis, which in turn affects treatment effect and prognosis. In this article, the authors review the molecular biological characteristics of CircRNA and its role in DNA damage repair, especially DNA double-strand break damage repair, and prospect the practical use in further treatment, prognosis and alleviation of adverse reactions of patients.