Wet flue gas desulfurization using a magnesia slurry sorbent in coal-fired power plants has been used because of its high SO2 removal efficiency and reliable and low utility consumption. The regeneration of MgSO3 center dot 6H(2)O byproduct to form magnesia is one of the key technologies to achieving environmental friendliness and low cost for this process. In this paper, the thermal decomposition behavior Of MgSO3 center dot 6H(2)O byproduct was investigated by the thermogravimetric analysis (TGA) method. The overall decomposition process can be divided into four phases. The observed mass loss in the first phase of dehydration is about 19-22 wt %, and the mass value of the final residual is 41-45 wt %. X-ray diffraction analysis for four phases was also conducted to assist the understanding of sample composition and its decomposition process. The thermogravimetric kinetic parameters were calculated using the Ozawa-Flynn-Wall method and the Coats-Redfern integral equation. The decomposition mechanism of MgSO3 center dot 6H(2)O byproduct can be concluded as the assumed random nucleation and its subsequent growth, with the best estimated value of 319.8 kJ/mol for the activation energy of thermal decomposition.