Target RCS fitting extrapolation is one of the effective means to save storage space of target RCS database. In this paper, based on the target echo data obtained by FEKO and the classical spectral estimation algorithm, a frequency full angle extrapolation of RCS of a typical missile warhead target is performed. First, based on the simulation data of 1~2 GHz, the parameters of the GTD (geometric theory of diffraction) scattering center model is extracted. Secondly, the RCS of the warhead target at 3 GHz and 4 GHz is extrapolated by using the proposed method. Finally, the extrapolated data are compared with the data obtained by FEKO, and the accuracy and the reliability of the extrapolation method proposed are verified. The simulation results show that the extrapolation results and the simulation results of FEKO are a highly similarity on the overall trend and at the strong scattering points, which can also be used to effectively describe the scattering characteristics of radar targets. The proposed method provides a theoretical support for RCS frequency full angle extrapolation and has a wide application in military.