The Terahertz (THz) absorption spectra of some short-chain peptides have been measured using a THz-FTIR at room temperature. Compared with the spectra in the mid-infrared region the THz absorption features were remarkable sensitivity to the chain-length dependence and sequence dependence. With the length of the peptide increasing the sharp spectra features became broadening. And the peptide and its reverse sequence produced a different and identifiable spectrum. These results demonstrate that the THz-FTIR is a promising method for studies on the low-frequency spectra of peptides.