2,6-diamino-3,5-dinitropyrazine-1-oxide(LLM-105),a novel explosive with high energy and low sensibility.In order to study the molecular structure characteristics of the explosive,the absorption spectra of LLM-105 in the frequency range of 0.2 ～2.4 THz were detected by terahertz time-domain spectroscopy(THz-TDS).The results showed that a number of characteristic absorption peaks with different intensity located at 1.27,1.59,2.00,2.08,2.20,2.29 THz.The article also simulated the absorption spectra of LLM-105 molecular crystal within 0.2～2.5 THz region by using Materials Studio 6.0 software based on density functional theory(DFT),and the simulated results agreed well with the experimental data except for the peak at 2.29 THz,which verified theoretically the accuracy of the experimental data.In addition,the vibrational modes of the characteristic peaks in the experimental absorption spectra were analyzed and identified,the results showed that the forming of the characteristic absorption peaks and the molecular vibration were closely related,which further provided important laboratory and technology support for the study of the transformation of molecule structure of LLM-105.There was no simulated frequency agreed with the experimental absorption peak at 2.29 THz,which may be caused by the vibration of the crystal lattice or other reasons.