The principle and composition of terahertz time-domain spectrum systems were described, and a terahertz time-domain spectrum system ranged from 0.1 THz to 3 THz was developed. The characters and predominance of terahertz time-domain spectrum technology on explosive identification were introduced and a mathematical model and a method for the explosive identification were proposed. The terahertz time-domain spectrum system was used to test the character absorbing spectra of explosives and main absorbing spectra were regarded as standard templates. Then, four kinds explosives(RDX,CL-20,LLM-105 and FOX-1) were put behind the barriers (soil, cement and plastic),and the terahertz time-domain spectrum system was used to obtain the character absorbing spectra of explosives penetrating through the barriers. The results were compared with standard templates to implement the explosive identification. The character absorbing spectra of RDX were obtained, and their character frequencies are 0.82, 1.70 and 2.40 THz. Furthermore, these explosives were tested through different barriers with different thicknesses. The results show that character absorbing spectra of explosives penetrating through the barriers match the standard templates perfectly, which verifies that it is feasible to use the terahertz time-domain spectrum system to realize explosive identification according to character absorbing spectra. Moreover, the terahertz time-domain spectrum system can be used to identify the residual trace of explosives and explore the imaging technology for penetrating through barriers.