The absorption spectra of TATB, in the frequency range of 0.2-2.5 THz, were measured by terahertz time-domain spectroscop, and the experimental results show that the characteristic peaks of TATB are located in 1.65 THz and 2.22 THz. The theoretical simulation by density functional theory(DFT) shows that the characteristic peaks of TATB are located in 1.2 THz and 1.65 THz. The experimental results agree with the theoretical calculation results, which show that TATB has distinct characteristic absorption peaks in the frequency range of 0.2-2.5 THz.