Via THz Time domain spectroscopy, the characterization of high conductive n-type, 1.31Ω cm silicon can be measured by directly analyzing the multiple reflections using Fabry-Perot theory. The magnitude and phase difference of total transmission show good agreement between theoretical and experimental values over a 2.5 THz frequency range with complex index of refraction and power absorption. The measured absorption and dispersion are strongly frequency-dependent, and all of the results are well fit by a Cole-Davidson type distribution