Abstract: This paper deals with four methods of real-time simulation of RF echo signal of 3D targets:the adoption of special hardware accelerating cards to calculate RF echo signal in real-time; the use of multi-computers' system to calculate RF echo signal in real-time; the adoption of autoregressive (AR) model or 3-spline to extrapolate or interpolate RF echo data; the use of scattering centers extracted from inverse synthetic aperture radar (ISAR) image to calculate RF echo signal. The differences of suchmethods are analyzed.