The key problem for the removal of SO2 by electrical discharge methods is how to obtain the hydroxyl radicals at high concentration and large production rates. With the micro-gap discharge method, O-2 and H2O in simulated gas streams (N-2/O-2/H2O/SO2) are ionized into a large number of OH. radicals to oxidize SO2 into SO3 which reacts with H2O forming H2SO4 droplets at 120 degrees C in the absence of any catalyst or absorbent. The droplets are captured with an electrostatic precipitator. As a result, conversion of SO2 to primarily H2SO4 is limited by the generation of OH. radicals. By increasing the reduced field and concentrations of O-2 and H2O, the amount of OH. radicals increase resulting in more removal of SO2 from gas streams. The removal efficiency of SO2 reaches 100% when the residence time is only 0.74 s. Therefore, a new gas-phase oxidation method for removal of SO2 without NH3 additive is found.