Absorption process of SO2 by carbide slag slurry in spray tower was studied in this work.The results show that with increase of SO2 concentration in flue gas its removal rate is a volcano curve.When pH value changes from 3 to 13，the removal rate of SO2 goes up from 52.3% to 94.7%.Increasing concentration of carbide slag slurry and decreasing their grain diameter can improve absorption of SO2. When L/G increases from 10 L·m-3 to 50 L·m-3，the removal efficiency puts up by 59.9%，but drops by 14.3% while L/G was continually raised from 50 L·m-3 to 80 L·m-3.A mathematics model is built based on the chemical reaction of desulfurization by carbide slag，the overall reaction order n=α+β=1.67，the activation energy Ea=51396.59 J·mol-1 and the frequency factor k0=0.37894×106 (mol·m-3)-0.67·s-1.