Thermal decomposition reactions of dolomite samples from Wansheng area of Chongqing were investigated by the simultaneous TG/DTG experiments to reveal the thermal decomposition mechanism and influential factors. The results show that the thermal decomposition process of dolomite samples follows the three-dimensional diffusion (three dimensional particle shape, Jander equation) model, and the value of the activation energy for the thermal composition is 357.4 kJ/mol. The kinetic model of the thermal decomposition process has been established based on the research results. The contrast experiments of the influential factors show that the value of the activation energy for the thermal composition would be increased significantly with the decrease of sample particle size and the increase of sample weight; nevertheless, the change of the SiO₂ content of dolomite and the flow rate of protective gas has little impact on the activation energy of thermal decomposition of the dolomite samples.