The stability of titanite is controlled by pressure, temperature, compositions of the bulk rock and the coexisting fluid, activity of H2O, fugacity of O2. Titanite is a common accessory mineral in a large range of rocks. It is widespread in magmatic rocks with high Ca/Al ratio. It appears in different metamorphic rocks ranging from greenschist facies, blueschist facies and amphibolite facies. Its stability may extend into eclogite-facies and high-pressure granulite-facies in calcic rocks. Because of its high U in its structure and high closure temperature (upper limit of amphibolite-faces), titanite is an ideal U-Pb dating mineral. In contrast to zircon, titanite (composed mainly of Ca and Ti) is quite reactive in most rocks contain Ca and Ti at different conditions. Therefore, its U-Pb ages are likely to yield the age of metamorphic crystallization rather than resetting by simple diffusion, such that metamorphic titanite may preserve complicated U-Pb system that contains information of the whole metamorphic history of the rock, which can be revealed by in situ U-Pb dating, e.g., SHRIMP, LA-MC-ICP-MS and LA-ICP-MS. Importantly, Zr concentration in titanite is sensitive to temperature and pressure, and accordingly Zr concentration in titanite is a good thermobarometer. Both mineral assemblages in equilibrium with titanite and titanite-Zr thermobarometer can be used to determine pressure and temperature. Consequently, P-T-t paths of metamorphism can be defined in combination with U-Pb titanite ages.