Terahertz time-domain spectroscopy (THz-TDS) and density functional theory (DFT) simulation are adopted to study the spectral properties of arabinose chiral isomers in the terahertz band. It is found that L-, D- and DL-arabinose show their characteristic absorption peaks in the effective spectrum range of 0.4-1.8 THz, and the absorption spectra of the three arabinoses are obviously different. The absorption spectra of L-, D- and DL-arabinose are calculated with the use of density functional theory in Gaussian09 software, and the characteristic absorption peaks are identified. The results show that the theoretical simulation is consistent with the experimental result and terahertz time-domain spectra can be used to identify the arabinose chiral isomers and their racemic compounds. This indicates that the correlation between chiral isomers and their terahertz spectra can be revealed by terahertz time-domain spectra. So terahertz time-domain spectra provide a new method for studying the detection and analysis of chiral isomers and their racemic compounds.