Abstract: Radiation therapy is an extensively applied cancer treatment methods in clinic. Radiation therapy can be conducted by either administrating/implanting radioactive isotope agents into the patients to irradiate tumors from inside, or using external beams (e.g. X-ray beams) to irradiate the tumor from the outside. It is well known that oxygen molecules play an important role in enhancing radiation-induced cancer cell killing. However, as most of solid tumors possess hypoxic tumor microenvironment, the tumor hypoxia is well recognized as one of important reasons that lead to the resistance of tumors to radiation therapies. In recent years, owing to the rapid development of biomaterials and nanotechnology, many different strategies have been reported to effectively modulate and reverse the hypoxic tumor microenvironment. In this article, we will summarize various types of nano-biomaterials for tumor hypoxia relief and their application in radiotherapy sensibilization, as well as the future clinical translation.