Oxygen diffusion in minerals and accompanied isotopic exchange inclosed systems are discussed with special application to geospeedometry. The extent of either intractrystalline or intercrystalline isotopic re equilibration by oxygen diffusion in minerals is ascribed to different cooling rates at which igneous rocks were cold from high crystallization temperature or metamorphic rocks from peak metamorphic temperature. According to the models of oxygen diffusion and isotopic exchange in minerals(i.e., Giletti model and Eiler model), the cooling rate of rocks can be calculated from the measured δ 18 O values, modal abundences and grain sizes of major rock forming minerals. Case studies are presented to elucidate the effect of oxygen diffusion on isotopic composition in minerals and its application to determination of cooling rate.