The interaction between plasma and electromagnetic wave mainly lies in four aspects, the incident electromagnetic wave′s reflection, absorption, dispersion and modulation by plasma. The features of plasma and its effect on electromagnetic wave propagation are introduced. Simulation model is built based on finite difference time domain (FDTD) method. Adjusting characterization parameters of plasma, the effects on the scattering physical mechanism and propagation characteristics of incident microwave from symmetrical and asymmetrical plasma cylinders are simulated and analyzed. Simulation results show that frequency and collision frequency of plasma are determined by its density, while frequency and collision frequency are the main elements that influence plasma′s electromagnetic scattering characteristics.