Abstract: In the current situation of the increasingly serious terrorist activities, explosives were hidden inside the package by terrorists. The main task for international anti-terrorism is to detect the explosives hidden in the package timely and precisely. The chemical elemental composition of explosive is mainly C, H, O and N. Daily necessities are also composed of these four elements. There is a great difference for elemental ratio between daily necessities and the explosive. The atomic density and relative content of C, H, O and N can be determined, which can distinguish explosive from organics. A removable explosive detection device based on tagged neutron method was developed. The tagged neutron method (TNM) technique is mainly based on the principle of coincidence to reduce the background of spectrum. The contents of chemical elements (C, N, O) and the ratio of C/O and C/N in the explosive were determined by analyzing the characteristic gamma energy spectrum to determine the existence of explosives. The ING-27 neutron generator and Φ76×76 mm LYSO scintillator detectors are selected in the experiment. Explosives detection devices are used to measure the sample of explosives surrogate, organic and explosives placed behind organic in the package. The results show that this method can effectively distinguish between explosive TNT and organic dry milk powder.