Abstract: The influence of the plasma around the warhead,which may have influenced the radar scattering characteristic of the reentry targets,is analyzed,based on the micro-wave attenuation mechanism of the plasma. This paper does the research to calculate the parameters of the plasma in formula firstly,getting help from the electromagnetic simulating software FEKO and making use of the method mixed fast multipole algorithm with physical optics,and then simulates the cases about the influence on RCS of parameters of plasma. The simulation results show that the RCS value of warhead in the reentry phase,when the target is coated by plasma, is effectively lower than there is nothing around. Also the simulation brings certain effect to the antimissile system in target-detecting and the penetration of ballistic missile.