To address the issue of ammonium dinitramide (ADN)’s strong hygroscopicity that restricts its engineering application, an ADN/hexamethylenetetramine (HMTA) cocrystal was prepared and its properties were studied. The cocrystal was synthesized using the solvent evaporation method. Its crystal structure, purity, thermal properties, energy performance, mechanical safety, and hygroscopicity were systematically characterized by single crystal X-ray diffraction (SC-XRD), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), simultaneous thermal analysis (TG-DSC), oxygen bomb calorimetry, BAM impact/touch sensitivity tests and hygroscopicity tests. The 2D fingerprint was constructed with Crystalexplorer to study its intermolecular interactions. The results showed that the asymmetric unit of the cocrystal contained two ADN molecules and one HMTA molecule, belonging to the monoclinic crystal system with the C2/c space group, and had a density of 1.564 g·cm-3. The analysis of intermolecular interactions effectively confirmed the formation of N?H···N hydrogen bonds with shorter bond lengths and greater strength in the cocrystal. XRD and EA confirmed that the cocrystal was a pure phase with a molar ratio of ADN to HMTA of 2:1. In terms of thermal properties, the melting point of the cocrystal was 130.2 ℃, 38.8 ℃ higher than that of ADN, and the initial decomposition temperature was 168.5 ℃, 14.2 ℃ higher than that of ADN. Regarding energy performance, the formation enthalpy of the cocrystal was -492.55 kJ·mol-1, the theoretical specific impulse value was 201.07 s, the detonation velocity was 7854 m·s-1, and the detonation pressure was 20.72 GPa. In terms of mechanical safety, the friction sensitivity was 288 N and the impact sensitivity was greater than 50 J, both higher than those of ADN. In terms of hygroscopicity, the hygroscopicity rate of the cocrystal was 0 after 153 h at 25 ℃ and 70% relative humidity, while the hygroscopicity rate of ADN reached 20.95% after 48 h. The conclusion indicates that the preparation of the ADN/HMTA cocrystal effectively solves the problem of ADN's strong hygroscopicity.