Abstract: In the field of arms control verification techniques, the dismantlement authentication techniques of nuclear warheads mainly involve the studies of the detection and authentication methods of the special nuclear material and high explosive of nuclear warheads before and after the dismantlement of nuclear warheads. In this paper, an element analysis method of the explosive in WgU warheads (nuclear warheads with weapons-grade uranium cores) based on thermal neutron analysis, namely EAMEUW-TNA, was proposed. The calculation method of the element number ratios of explosive was deeply analyzed, and the numerical simulation platform of the EAMEUW-TNA was established based on the JMCT software and used to study the feasibility and the effect of the EAMEUW-TNA. The results show that the EAMEUW-TNA has high reconstruction accuracy of the element number ratios, and can be used to judge whether there exists explosive in the WgU warhead.