Ultrafine and spherical ε-CL-20 particles were prepared by the spray and ultrasound-assisted recrystallization device.The morphology, particle size and crystal type of the samples were characterized by scanning electron microscopy(SEM) and X-ray diffraction(XRD).The thermal stability of the samples were analyzed by differential scanning calorimetry(DSC).The apparent activation energy of thermal decomposition reaction and critical temperature of thermal explosion were calculated by Kissinger′s method and Zhang-Hu-Xie-Li′s formula.Their mechanical sensitivity were tested by GJB772-1997 method.Results show that prepared ultrafine CL-20 is spherical particle with size of about 400nm and have a good dispersibility.The crystal type of the ultrafine CL-20 is epsilon(ε).The thermal stability of ultrafine CL-20 is lower than raw material CL-20.The critical temperature of thermal explosion of raw material CL-20 and ultrafine CL-20 is 242.85 ℃ and 241.64 ℃, respectively.The apparent activation energy of raw material CL-20 and ultrafine CL-20 is 156.04 kJ·mol^-1 and 165.11 kJ·mol^-1 respectively.Compared with raw material CL-20, the impact sensitivity of ultrafine CL-20 decreases significantly, the characteristic drop height (H₅₀) increases from 14.98 cm to 31.95 cm, the friction sensitivity of ultrafine CL-20 also decreases, the explosion probability decreases from 100% to 40%.