The thermal decomposition processes of CL-20 nanoparticle (NP), core-shell structured CL-20@Al NP, and CL-20@AlO NP were studied through reactive molecular dynamics simulations. The results are as follows: (1) the CL-20@Al and CL-20@AlO NPs decomposed earlier than the CL-20 NP; (2) the Al shell experienced the melting-aggregation process and gradually changed from a shell structure to block aluminized clusters; (3) different in the decomposition of the CL-20 NP, N₂ appeared first in the decomposition of the CL-20@Al and CL-20@AlO NPs, indicating that Al changed the initial decomposition process of CL-20; (4) the quantities of NO₂, NO, and CO₂ produced during the decompositions of the CL-20@Al and CL-20@AlO NPs were much lower than those produced during the decomposition of CL-20 NP. This occurred because the Al atoms had high activity at high temperature and attacked these products to produce massive aluminized substances; (5) Al significantly promoted the movement of H and N atoms but impeded that of O and C atoms in the three systems. This study will present fundamental information about the interfacial behaviors of aluminized explosives.