Semi-dry desulfurization ash has become an environmental problem in China. Oxidation of CaSO3 in desulfurized ash to CaSO4 instead of natural gypsum is the main way of resource utilization. ethod: In this study, CaSO3•2H2O, 10%CaCl2-CaSO3 2H2O, and 0.6%Fe2O3-CaSO3•2H2O were employed as the objects. TG and DSC thermal analysis kinetics and Kissnger, Ozawa, Crane, and Coasts – Redfern equation non-isothermal kinetics analysis methods were performed to explore the oxidation kinetics characteristics of CaSO3 and their mixture. The oxidation process and gas-solid reaction mechanism of CaSO3 were analyzed, and the most probable mechanism function and kinetic parameters of the reaction were calculated. The results demonstrated that the oxidation of CaSO3•2H2O and 0.6%Fe2O3-CaSO3 2H2O can be divided into two stages. CaSO3•2H2O loses crystal water and oxidizes to generate CaSO4 and release heat, which belongs to the gas-solid reaction controlled by three-dimensional diffusion. The former Eα is 205.5 KJ•mol-1 and A is 6.791×1012 s-1. The latter Eα is 195.62 KJ•mol-1, and A is 2.51×1012 s-1. The peak temperature of DSC curve of the former is lower, indicating that Fe2O3 promotes the oxidation reaction. The oxidation of 10%CaCl2-CaSO3•2H2O is different from the above two substances, and belongs to the gas-solid reaction mechanism controlled by three-dimensional diffusion (spherically symmetric). The reaction can be divided into three stages. The peak temperature corresponding to DSC curve is higher than the first two, indicating that CaCl2 inhibits the oxidation reaction. The Eα is 243.98 KJ•mol-1, and the A is 5.67×1015 s-1.