It has been proved that the antimalarial agent, Artemisinin and its derivates (such as artemether, arteether, artesunate, dihydroartemisinine, etc) boast powerful antitumor effects. Recently, researches have found that Artemisinin and its derivates can also enhance the radio-sensitivity of tumors through regulating cell cycle, creating cytotoxic effects induced by ROS, suppressing GSH activity and inhibiting the reparation of DNA damage etc. Moreover, they can reduce cell survival in a dose-dependent manner. This paper is paying more attention on the radio-sensitizing effects, characteristics and mechanisms of artemisinin and its derivates.