To refine the hexanitrostilbene(HNS), nanometer HNS explosive with average particle size of 94.8 nm was prepared by a high energy ball milling method. The characteristics and analysis of the HNS sample were performed by scanning electron microscopy(SEM), X-ray diffractometry(XRD), infrared(IR) spectroscopy, X-ray photoelectron spectroscopy(XPS), DSC-IR analysis and 5s explosion temperature. Results show that after ball milling, the micro morphology of the explosive is nearsr-pherical, and the particle reveals a normal distribution. The mechanical ball milling action does not change the original crystal form, molecular structure, and surface elements of HNS, showing that mechanical milling is a kind of reliable method for fabrication of nanometer HNS.The apparent activation energy of thermal decomposition of nanometer HNS is 12.4 kJ·mol^-1 higher than that of raw HNS, indicating that the activation of nano HNS molecules requires a higher energy. After heating, nanometer HNS decomposes into a large number of CO₂ and a small amount of H₂O, while the N element is present in the non polar N₂ molecule. The 5 s explosion temperature of nanometer HNS is 12.2 ℃ higher than that of raw HNS, meanting than the nanometer HNS has lower thermal sensitivity.