Abstract: The microwave desulfurization experiment is carried out by adding additives to Xinyu coking coal.In the microwave frequency at 2.45 GHz,acidic auxiliary(HCI),alkaline auxiliary(NaOH),reducing auxiliary(HI)and oxidizing auxiliary(HCOOH-H₂O₂)are obtained desulfurization rate combined with the Xinyu coking coal,and the transmission and reflection method is used to measure the dielectric constants of coal samples before and after microwave desulfurization in the frequency range of 0.1-6.5 GHz to characterize the changes in the dielectric properties.The results show that the relative permittivity, relative medium loss factor and medium dissipation factor of the coal sample increase with the increase of the concentration of hydrochloric acid solution in the range of 0.1-6.5 GHz; the relative permittivity of the coal sample after sodium hydroxide solution treatment decreases with the increase of microwave frequency; the relative permittivity curve of the coal sample treated with the hydroiodic acid solution slowly decreases with the frequency increase; after the formic acid-hydrogen peroxide solution treatment, the relative permittivity curve of the coal sample tends to be stable and does not gradually decrease with the increase of the frequency, and the curve starts to rise after 6.0 GHz.