Abstract: Electromagnetic inverse scattering(EMIS) has been widely used in nondestructive testing and biomedical imaging. In this paper, the inverse scattering imaging problem of conventional media is extended to the inverse scattering problem of dispersive media, and the nonlinear relationship between plasma scattering field and plasma parameters is studied. An inverse scattering method based on subspace-based optimization method (SOM) and postprocessing of data is proposed to reconstruct the dispersive medium plasma described by Drude model. For the multi-solution problem caused by the nonlinear relationship between the collision frequency and the plasma dielectric constant, the collision frequency reconstruction formula is modified to determine the unique solution. In addition, in order to improve the inversion accuracy of collision frequency, the inversion method is improved by using the reconstruction results of plasma electron density with high accuracy. Simulation results verify the fast convergence and robustness to noise of the proposed method. This study can provide an efficient and stable method for plasma parameter reconstruction.