To research the influence of aluminum (Al) on the decomposition of 1,3,5-trimethylene trinitramine (RDX), a type of superfine RDX/Al composite as an energetic material with a mass ratio of 70/30 was successfully prepared by mechanical ball-milling method. The morphology and structure of the superfine RDX/Al composite were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The thermal decomposition properties were analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal-infrared spectrometry (DSC-FTIR) online. The results showed that the as-prepared material was a type of a novel superfine composite with the superfine RDX particles coated on the surface of Al flakes. XPS analysis indicated that a new Al-N bond was formed in the superfine RDX/Al composite and both physical and chemical absorptions existed between RDX and Al at the same time. The thermal decomposition temperature of RDX in the superfine RDX/Al composite had a shift of about 50 °C towards the lower temperature range compared with that of the neat superfine RDX when tested at four heating rates of 5, 15, 25 and 35 °C min -1 . Its activation energy value also decreased to 70.8 kJ mol -1 compared with that of the neat superfine RDX (119.6 kJ mol -1 ). Moreover, thermal sensitivity of the superfine RDX/Al composite increased. DSC-FTIR analysis showed that the main decomposition products of the superfine RDX/Al composite were N 2 O and CO 2 with nearly no NO and NO 2 detected. The formation of Al-N bond and reactive Al atoms are the main reasons for the notably advanced decomposition of RDX in the superfine RDX/Al composite.