Abstract: To understand the interaction mechanism between electromagnetic waves and reentry plasmas and the effect on the reentry communication and scattering characteristic of reentry vehicles,a piecewise linear current density recursive convolution finite-difference time-domain(PLJERC-FDTD) algorithm was applied to study the scattering characteristic for the hypersonic flow fields of conductive metal semi-sphere.The effects of incidence wave frequency,scattering angle,Mach number and altitude on the radar cross section(RCS) were analyzed.The results demonstrate that the forward RCS is the maximal RCS of all scattering orientations.The backward RCS and the bistatic RCS of flow fields vary little with Mach number and altitude for L and S wave band when the Mach number is not more than 10 in this article,and the margin of the backward RCS and the bistatic RCS between flow fields and semi-sphere is small.The forward RCS of flow fields is more than that of semi-sphere for L and S wave band because of the over-dense plasma shell when the Mach number is 14 or 16 in this article,and the difference of the bistatic scattering characteristic between flow fields and semi-sphere is obvious.