In order to develop a scale-up and continuous preparation method， the microchannel crystallization technology based on solvent/non-solvent method has been used to prepare hexanitrohexaazaisowurtzitane/octogen （CL-20/HMX） co-crystal. The field emission scanning electron microanalyzer （FE-SEM）， X-ray powder diffraction （XRD）， Raman spectroscopy， Fourier infrared spectroscopy （FT-IR）， thermal analysis and sensitivity test were applied to characterize and analyze the morphology， structure， thermal performance and sensitivity of samples. Results show that this method has successfully prepared CL-20/HMX co-crystal. Its apparent morphology is the flower clusters with a diameter of 20-30 μm， assembled by platelet crystals with thickness of 200-600 nm， accompanying individual flaky crystals （thickness of 200-600 nm）. The CL-20/HMX co-crystal prepared by microchannal crystallization has only one sharp exothermic decomposition peak during the exothermic process. Its exothermic peak temperature is at 243.4 ℃， which is lower than that of the raw materials CL-20 （250.2 ℃） and HMX （284.7 ℃）. Its temperature range of thermal decomposition is only from 242.7 to 246.0 ℃， much narrower than those of raw CL-20 （230.0-254.6 ℃） and HMX （281.0-290.7 ℃）， which means a higher energy release efficiency. Its apparent active energy is 470.75 kJ·mol^-1，falling between CL-20 （175.04 kJ·mol^-1） and HMX （481.45 kJ·mol^-1）， which is 297.29 kJ·mol^-1 hagher than that of raw CL-20，indicating a good thermal stability. Its impact sensitivity is 18 J， which is 8 J and 3.6 J higher than those of raw CL-20 （10 J） and HMX （14.4 J） respectively， and the friction sensitivity is 20% lower than that of raw CL-20. The sensitivity results show the safety of the CL-20/HMX co-crystal has been improved compared with the raw materials.