Ionizing radiation (IR) can cause immune dysfunction, resulting in severe damages to human health and affecting the recovery of radiation injury. Dendritic cells (DCs) are the most potent antigen presenting cells (APCs), which are also the initiator and modulator of immune system. Studies on the radiation effects of DCs can not only help to understand the mechanism of radiation-induced immunosuppression, but also facilitate the research on DCs function for radioprotection. DC-based cancer vaccine combined with radiotherapy also provides new insights into cancer therapy. This paper reviews the influence of IR on the viability, phenotype, antigen presenting function and migration capacity, cytokine secretion of DCs, as well as the underlying mechanism. We also review some advances in tumor therapy by combining DC vaccine with radiotherapy, hoping to provide reference for studying radiation-induced immunosuppression and radioprotection.