Abstract: In order to detect the chemical weapon contained in the unmarked ammunition, a fast neutron chemical weapon detection system based on associated particle technology (APT) was developed. The detection system included an associated particle DT neutron source, an particle detector, a detector and shielding as well as an electronics signal acquiring and processing system. Four types of chemical weapons including sarin, VX reagent, mustard gas and adamsite reagent were measured by the detection system. The characteristic gamma spectra induced by 14 MeV neutron were obtained. According to the analysis of the spectra, the characteristic gamma peaks of phosphorus (P), fluorine (F), sulfur (S) and chlorine (Cl) were clearly measured except arsenic (As). These results showed the APT could reach the goal of nondestructive detecting chemical weapon.