Abstract: The heavy ions are the ionized particles that are heavier than element He of second one in the element periodic table. Because of the strong local ionization on the pathway of penetration,the high-energy heavy ions induce the biological effects of more serious radiation damage compared with the traditional photon radiation,such as X-rays or γ-. The researches onmechanism show that radiation by heavy ions results in multiple-type and multiple-number damages at one or two helixes of DNA,i.e.,the clustered DNA damage. The complex damages impede the binding of DNA repair enzyme with DNA segment and the consequent repairing of cells,resulting in the subsequent death of cells or improper repair（i.e.,mutation）. The characteristic of heavy ion radiation,easily inducing mutant,is popular in mutation breeding of plant and microorganism. In addition,due to the high cell killing capability and the advantage of inverted dose profile,the exact targeted therapy can be achieved using heavy ions to treat tumor,because it delivers high doses of radiation to the deep regions of tumor cells to efficiently kill them but causes relatively little damages to the surround tissues at low dose;thus,heavy ion beam is deemed a most promising technology of tumor radiotherapy. Here we review and deeply analyze the clustered DNA damage induced by heavy ions and its repairing mechanism,as well as the research advances on the 2 key repair pathways. Besides,we summarize the application of heavy ions in mutation breeding and cancer therapy. It is expected that this review may provide a convenience for researchers in radiation biology of heavy ion to understand clustered DNA damage and repair mechanisms,and culture the research direction for better estimating the risks of heavy ions to human health and setting up better protection strategy as well as the application in life science.

Key words: heavy ions, clustered DNA damage, radiation-induced breeding, heavy ion radiotherapy