The non-thermal plasma created by high voltage pulsed power supply can be used to remove sulfur dioxide in the air, but how to increase the removing efficiency is not clear. It is novel to apply the magnetic field in removing S02 as discussed in this paper. The mechanisms of removing sulfur dioxide by non-thermal plasma along with the application of the magnetic field are analyzed, and the related factors affecting the removal efficiency, such as the magnitude of pulsed voltage, the polarity of the pulse, the layout of the discharge electrode, especially the magnetic field are experimentally investigated. It can be concluded that the purification efficiency is improved significantly by applying the magnetic field.