Abstract: In order to clarify the influencing factors of dielectric properties change with coal high sulphur desulfurization by microwave radiation,the collaborative method of 2. 45 GHz microwave and HAc-H₂O₂ for coal desulfurization was chosen,the sample components was analyzed and characterized by XRD and XPS,the corresponding model compounds was selected according to the results of the composition analysis,the permittivity of coal and model compounds were measured in 0. 5-18 GHz range of frequency,The results showed that: he dielectric properties of coal had obvious differences in 9-12 GHz and 13-18 GHz frequency before and after the experiment,the dielectric loss is reduced in both frequency bands,the permittivity measuring reflected that pyrite and other mineral components had obviously affect on dielectric properties of coal in the 13-18 GHz,and organic sulfur compounds represented by small solid molecules of thiol,sulfide,sulfoxide,sulfone and thiophene had weaker affect on dielectric properties of coal in the 9-12 GHz,the coupling capabilities of the organic sulfur model compounds to microwave were sulfone（sulfoxide） ＞ thiol（sulfide） ＞ thiophene,the magnitude changes of molecular dipole moment calculated by the software named material studio were the same,this complied with that the greater the dipole moment was,the stronger the responses to microwave.