Abstract: According to the planar surface wave plasma source, the model of slot antenna radiating electromagnetic waves is built. The electromagnetic field distribution of slot antenna array radiating is simulated and compared with surface wave, the discharge mechanism of planar surface wave plasma is analyzed. The results show that the electromagnetic field excited by the whole slot antenna array is the linear superposition of each slot antenna excitation field; the electromagnetic field radiated by the slot antenna array only near the waveguide wall is big enough, and decays rapidly with the increase of distance; the electric field of slot antenna array and surface wave are much larger than the respective magnetic field, which can be neglected when analyzing the role of electric and magnetic fields on charged particles; the electromagnetic field of the surface wave is much larger than the field of the slot antenna array, the strong electromagnetic field range of the surface wave is much greater than that of the slot antenna array, plasma can enhance electromagnetic fields and expand the range of strong lectromagnetic field.