A novel composite microsphere of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) and 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) were fabricated by spray drying technology. The morphology, structure and thermal behavior of the obtained particles were characterized via scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), powder x-ray diffraction (PXRD) and differential scanning calorimetry (DSC). SEM results demonstrated that LLM-105/CL-20 microspheres in range of 1-3 mu m are relatively uniform. PXRD and FT-IR indicated that the peak patterns of the composite LLM-105/CL-20 has shifted slightly from the raw material. Thermal analysis implied that energetic microspheres LLM-105/CL-20 has lower decomposition. In addition, a possible formation mechanism for energetic microsphere was proposed. Moreover, the impact sensitivity of composite microspheres could be reduced 5 times compared to the raw CL-20. This work may introduce a novel idea towards fabricating the composite microspheres.