Experimental measurement and theoretical analysis of terahertz spectrum for one pure material and some mixed explosive samples are introduced. The refractive index and absorption coefficient of the samples are measured in the region of 0.2～2.5 THz by time-domain spectroscopy(THz-TDS). The absorption spectra are obtained correspondingly. Results indicate that the THz-TDS technology can identify the different explosives and roughly analyse the main ingredients of the mixed samples.