Oxidation of sulfite is all important process in flue gas desulfurization. The inhibitory effects of four inhibitors on the intrinsic oxidation of sulfite were compared, and ethanol was found to be all excellent inhibitor. The intrinsic oxidation kinetics of sulfite in the presence Of ethanol used as all inhibitor was investigated using a batch apparatus. The reaction orders of the reagents and the activation energy were obtained. The results indicate that the intrinsic reaction proceeds in two steps: rapid reaction in all oxygen-rich state and slow reaction in an oxygen-depleted state. Integrated with the macroscopic oxidation kinetics of calcium sulfite in the presence of an ethanol inhibitor, it was concluded that the macroscopic oxidation process is controlled by the intrinsic reaction rate and the intrinsic oxidation reaction proceeds in the rapid reaction state. Furthermore, a mechanism for the intrinsic reaction is proposed based oil a steady-state assumption. The results derived with this mechanism are in good agreement with the experimental results.