Safe disposals of high level radioactive-waste have become a serious problem for the sustainable and healthy development of the nuclear industry. Nuclear waste forms based on crystalline mineral phases have attracted great attention, because of their excellent performance. Among them, titanite or sphene (CaTiSiO₅) is proposed as a host phase for the immobilization of radioactive nuclides, especially high level of nuclear wastes, because of its good anti-radiation properties. Due to radioactive decay of radionuclides, especially α-decay, the crystal structure of titanite may be damaged and in the metamict, an aperiodic or amorphous state. In order to evaluate the physical and chemical properties and long-term stability of titanite solidification, it is necessary to study the irradiation damage mechanism of titanite. This paper reviews the main research achievements of titanite in recent years, which include the possible location of radioactive nuclides in its crystal structure, high temperature/high pressure-induced and radiation-induced phase transitions, infrared and Raman spectroscopy, synthesis methods, irradiation damage effect and damage mechanism, annealing induced recrystallization after metamictization, hydrogen behavior, leaching in solutions and so on. In addition, some scientific controversies, such as the crystal structure of metamict titanite in the atomic scale, the oxidation state of actinides in titanite, structural similarities or differences between metamict titanite and "glassy state titanite", the reason why high temperature cannot completely restore the crystal structure of metamict titanite, and the problem whether there is any recrystallization during low temperature hydrothermal reactions of radiation damaged titanite, are discussed and reviewed.