Microwave desulfurization capitalizes on the different dielectric properties of sulfur-containing and sulfur-free components in coal. However, the dielectric properties of thiophene compounds, the predominant sulfur species in coking coal, are not well understood. Herein, the dielectric properties of different thiophene model compounds containing coal-like compositions and structures are investigated under the impact of microwave frequency and temperature. The increases of aromaticity in thiophene compounds suppress their microwave responses to the electric irradiation, as indicated by the decrease of the loss tangent values, while thiophene compounds with polar functional groups exhibit higher microwave reactivity. Additionally, the oxidation of the functional groups in thiophene further increases the ability to absorb and convert the microwave energy to the thermal energy. The dielectric properties of thiophene compounds are also sensitive to the changes in microwave frequency and temperatures. The thiophene compounds exhibit a higher microwave adsorption capacity at the microwave frequency of 915 MHz relative to 2450 MHz, which is opposite to the trends for the penetration depths. Such an observation indicates that the desulfurization of thiophene compounds is more readily achieved at the frequency of 915 MHz. The findings associated with the dielectric properties of different thiophene compounds mark an important step toward optimizing the microwave desulfurization of coal.