Abstract: Sonic logging tool SKC-B is simulated with a numerical model in this paper and its two-dimensional spectra of full-waves is used to analyze the frequency characteristics of longitudinal, shear, and Rayleigh waves. Numerical results show that P-wave movemout is affected by the noises contained in the sonic waveform and S-wave movemout is impaired by pseudo-Rayleigh waves. Based on these results, calculation methods of P- and S-wave velocities are constructed.