The thermal safety of polymer bonded explosive (PBX) specimen based on HMX and their compatibility with contacted materials, silicone rubber cushion and polyurethane adhesive were investigated by on-line chemical reactivity test (CRT) detection device developed by the authors. The results show that the PBX specimen has a good thermal stability. The concentrations of CO₂ and N₂O evolvedfrom the specimen are only 0.1 mL·g^-1 after heated at 100 ℃ for 1.15 months. In comparison with PBX specimen, the concentration of N₂O evolved from PBX specimen/silicone rubber cushion or polyurethane adhesive mixture has a very little increase, but the net gas evolution quantity of the two mixtures is small, indicating that PBX specimen and two contacted materials are compatible.