Abstract: The effects of electron number density and its profile on the microwave propagation characteristics in a plasma slab are discussed. The incident wave travels vertically on the plasma slab. The plasma layer is modeled as adjacent, homogeneous sub-slaps, whose approximate distributions are linear or parabolic. The theoretical method to analyze the propagation of the wave is based on the stratified layer model and invariant imbedding principle. Multiple reflections between sub-slab interfaces are analyzed with the model. The numerical result shows that absorption with parabolic distribution plasma is better than the linear one, but the reflection is higher for the linear profile plasma. The power coefficient of reflection increases and the absorption coefficient decreases after an early peak