In this paper, the interaction between plasma and electromagnetic waves is studied. Itdemonstrates that high reflection coefficient requires low collision frequency and high plasmadensity. If its density is overdensed, the scattering characteristics of nonmagnetized collisionlesscold plasma and uletal conductor are comparable. As an example, the parameters of a plasmasphere with required RCS is given. The scattering characteristics of plasma with a large spacescale are also discussed.