Abstract: To enhance SO2 absorption rate and removal efficiency, hydrogen peroxide as a strong oxidant was added during the spray water humidification in the process of semi-dry flue gas desulfurization. The effects of hydrogen peroxide concentration, Ca/S mol ratio and approach to the saturation temperature on the SO2 removal efficiency were investigated. The results show that SO2 absorption rate can be significantly enhanced with hydrogen peroxide; when the lime particles are humidified by a hydrogen peroxide solution of 1.0% to 2.0%, the SO2 removal efficiency increases about 20% to 30%. Moreover, SO2 absorption rate and sorbent utilization increase with the hydrogen peroxide concentration.