Thermal behavior of the Shahreza dolomite ore is investigated in this paper. The hydration of the calcined dolomite was studied as a function of the calcination temperature. The DTA results exhibit three endothermic peaks at 800, 900 and 1050 °C, corresponding to decomposition of MgCO₃ and CaCO₃, both are present in dolomite and free calcite, respectively. The results also indicated that the degree of calcination is increased by increasing the calcination temperature from 800 to 1400 °C. As the calcining temperature increases from 800 to 900 °C, the hydration degree of the dolime increases too because of more humid absorbing phases produced at higher temperature. However, the hydration degree declines with further increase in the calcination temperature and became negligible when the sample is calcined at 1400°C probably due to  the sintering process occurred at elevated temperatures.