In order to investigate the effect of aggregation structure on the properties of hexanitrohexaazaisowurtzitane/octogen （CL?20/HMX） co?crystal， the droplet confined crystallization was used to prepare spherical CL?20/HMX co?crystal. The morphology and structure of the samples were characterized by field emission scanning electron microscopy （FE?SEM）， X?ray powder diffraction （XRD） and fourier transform infrared spectroscopy （FT?IR）. The properties of the samples were analyzed by thermal analysis， sensitivity and combustion tests. The results show that the spherical CL?20/HMX co?crystal was successfully prepared by this method. The diameter of the spherical CL?20/HMX co?crystal is 1.3-1.85 mm， the hollow ratio is about 40%， and the specific surface area is 6.890 m2·g-1. The exothermic peak temperature of spherical CL?20/HMX co?crystal is located at 245.8 ℃ ， the thermal decomposition activation energy （463.02 kJ?mol-1） and the critical temperature of thermal explosion （241.28 ℃） are higher than those of flake CL?20/HMX co?crystal， exhibiting the excellent thermal stability of spherical CL?20/HMX. The impact sensitivity is better than that of raw material and flake CL?20/HMX co?crystal， and the friction sensitivity falls between raw CL?20 and HMX， but lower than that of flake CL?20/HMX co?crystal. The ignition delay time is less than 8 ms and the combustion is efficient and stable， while the flake CL?20/HMX co?crystal， raw materials and their physical mixture exhibit flameless combustion.The construction of millimeter?sized hollow spheres for CL?20/HMX co?crystal has significantly improved the thermal stability，sensibility and combustion performances.