Microwave heating of double-layer porous medium is numerically investigated using a proposed numerical model. A two-dimensional domain composed of two porous layers is considered. The two porous layers have different particle sizes, porosities, thermal and dielectric properties. The generalized non-Darcian model developed takes into account of the presence of a solid drag and the inertial effect. The transient Maxwell's equations are solved by using the finite difference time domain (FDTD) method to describe the electromagnetic field in the waveguide and in the media. The temperature profile and velocity field within the media are determined by solution of the momentum and energy equations given by the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. This study focuses on effects of diameter, porosity, position and types of particles that have different thermal and dielectric properties. The computed results agree well with the experimental results. While the particle size and porosity mainly affect fluid flow within porous media, the thermal and dielectric properties strongly influence heat transfer mechanism in each layer of porous media. (C) 2013 Elsevier Ltd. All rights reserved.