This paper reports the spectral characteristics of histidine and arginine in THz range by calculation and terahertz time-domain spectroscopy (THz-TDS). Absorption peaks are found at 0.88，1.64，2.23 THz (for histidine) and 0.99，1.47，2.60 THz (for arginine) by THz-TDS，respectively. The vibrational absorption spectra of the two molecules are calculated based on semi-empirical theory in the range of 0.1—10 THz. The calculated spectrum exhibits many absorption peaks and the first three of them are well comparable with the experiment results in the range of 0.2—2.8 THz. The vibration rotation modes corresponding to the absorption peaks of the molecules are presented. These results mutually validated both approaches, and can further be used in identification of molecules and experimental research in wider effective spectral range.