Abstract: In order to have a better understanding of the reaction on the interface of mixed explosives under the femtosecond laser, a simulation model of the RDX/HTPB mixed explosive was constructed. Based on the ReaxFF-lg reaction force field, reaction molecular dynamics simulations were carried out under different laser loading conditions. The temperature and density variation of the system and the reaction characteristics at the interface were analyzed. The results show that when the laser energy is loaded from both ends of HTPB and RDX, there is no sharp temperature change at the interface of RDX/HTPB system. The higher the laser energy, the more violent the reaction between HTPB and RDX. At the interface, the H or C atoms generated by the decomposition of HTPB react with the small molecular products decomposed by RDX to form intermediate products such as CO, C₃O, C₂O₂, C₂HO, NH₂, NH₃, and final products such as H₂O, CO₂, and H_2.When laser energy is low, the reactions of RDX and HTPB are insufficient. There are still lots of undecomposed cyclic molecules in the RDX region, and HTPB region is mainly macromolecules in the form of long carbon chains, and the reaction between the decomposition products of RDX and HTPB in the interface region is insignificant.