The solvation of ions in aqueous media is a fundamental process in biology and chemistry, and the characterization of dielectric constant of aqueous electrolyte solutions at mi- crowave frequencies composes a powerful way to understand the dynamical process in aqueous media. In this work, we have combined the classical Debye and Drude models to determine the microwave conductivity of the salt (NaCl) solution by measuring its dielectric constant. We assume the permittivity of the electrolyte solution has a compound dielectric constant model which is the sum of the Debye model contributed by the water background and the Drude model accounting for the conductive ions in the solution. As a justification of the Drude model, the damping coefficient, γ, for the conductive ions need be far greater than the angular frequency, ω. From the DC conductivity measurement, we derive the damping coefficient of the conductive ions and prove the applicability of the Drude model in our experimental microwave regime from 0.1–20 GHz.