Abstract: When a reentry vehicle or a near space hypersonic vehicle reenters the atmosphere, its scattering characteristics would be significantly changed by the formation of plasma sheath and wake because of ionized air and ablation of the mass of the body. The Radar Cross Section (RCS) of the vehicle would be changed due to a number of effects associated with the plasma sheath and wake. So the scattering characteristics of near space vehicle are different to normal vehicle which is without the effect of plasma sheath and wake and it would be more difficult to be detected and tracked. Ballistic range is often be used to study the RCS of hypersonic vehicle.〓To deduce the real flying RCS of underdense turbulent wake from the experimental results of ballistic range, a scaling law is given in this paper. The scaling law is on the basis of binary scaling law for hypersonic flow and firstorder Born approximation for RCS analysis of underdense turbulent wake. Under these approximations, the scaling law shows the RCS proportion of underdense turbulent wake is σ1/σ2=η4 when D1/D2=η,V∞1=V∞2,ρ∞1/ρ∞2=1/η,ω1/ω2=λ2/λ1=1/η. The deduced scaling law would be useful the research of the RCS of underdense turbulent wake.