Abstract: The gradually accumulated information and knowledge regarding cancer stem cell or stem-like cancer cell greatly potentiated the research progression of radiation oncology and biology. In recent years, a series studies have uncovered that the cancer stem cell and cancer quiescent cell could be the major cells origin attributed to the radioresistance and recurrence of tumors in the course of radiotherapy. A rapid research progression has already been achieved respecting the radiosensitivity and related mechanisms of these two subsets of cancer cells, and which provides an idea strategy for development of the measures targeting tumor radioresistance. This paper reviewed and discussed the cellular basis and molecular mechanism of the tumor radioresistance from the aspects of cancer cells subsets and the radiobiological characteristics.