In this paper, a novel method to extract complex permittivity from synthetic aperture radar (SAR) images is proposed. The principle of the proposed method is outlined, followed by electromagnetic simulations, which is then verified by measurements. The simulation and measurement results show that the proposed method can accurately extract complex permittivity of a material-under-test (MUT), and generate high-resolution spatial map of this parameter. Measurement results also show that proposed method is capable of quantitatively resolving local inhomogeneity contrast. This makes the proposed approach a potential and good candidate for utilization in nondestructive evaluation (NDE) applications. The limitations of the proposed method are also discussed. Comparing to quantitative microwave and millimeter wave method based on inverse scattering techniques, this proposed method requires much less computational resources.