In order to investigate the characteristics of the reaction between ammonium sulfite. the main desulfurizing solution, and the flue-gas-contained sulfur dioxide during the process of ammonia-based WFGD (wet flue gas desulfurization) in a power plant, the gas-liquid absorption reaction between sulfur dioxide and an ammonium sulfite solution was studied in a stirred tank reactor. The experimental results indicate that the absorption of sulfur dioxide is controlled by both the gas- and liquid-films when the ammonium sulfite concentration is lower than 005 mol/L, and mainly by the gas-film at higher concentrations In the latter case, the reaction rates are found to be zero-order with respect to the concentration of ammonium sulfite The absorption rates of sulfur dioxide increase as the concentration of sulfur dioxide in inlet gas and the temperature increase. The reaction rate is of 0.6th-order with respect to the concentration of sulfur dioxide. (C) 2010 Elsevier Ltd. All rights reserved