Abstract: In order to solve the problem of radar cross section(RCS) simulation in the simulation test of radar detection of hypersonic target in near space, a target RCS reduction simulation method suitable for near space hypersonic vehicle under plasma sheath is proposed. Firstly, based on the relevant data of plasma frequency and electron collision frequency corresponding to different altitude and velocity, the relationship table of plasma frequency and electron collision frequency corresponding to different velocity and altitude was fitted. Secondly, the plasma frequency and electronic collision frequency corresponding to different target altitude and velocity are obtained by real-time table lookup under given radar frequency. The target plasma coating model and electromagnetic wave transmission model are established, and the attenuation coefficient and reflection coefficient of radar electromagnetic wave are calculated. Finally, the RCS reduction of target can be simulated by the attenuation coefficient and reflection coefficient of radar electromagnetic wave. By comparing with the concerned real data, the rationality of the method is proved. The simulation analysis shows that it is easier to obtain continuous tracks and shorter time to generate radar "black-out" by using high-frequency radar to detect near space hypersonic vehicle.