Possessing multiple energy levels, unique 4f electron transition ability and optical properties, rare earth elements can improve efficiently the activity of TiO2 photocatalysts by doping or preparing compound semiconductors. Furthermore, novel photocatalysts have been secured with RE elements. Based on relative documents, the application of rare earth elements in photocatalysts is reviewed in this paper, including RE modified TiO2 photocatalysts and non-TiO2 photocatalysts. The roles of RE elements and its mechanism, as well as the focus and outlook of the research of RE-containing photocatalysts were deeply discussed.