Two new copper complexes, [Cu(phen)2FOX-7](phen)NO3·4H2O and [Cu(phen)2FOX-7]Cl·3H2O (phen = 1,10-phenanthroline monohydrate; FOX-7 = 1,1-diamino-2,2-dinitroethylene) were synthesized and structurally characterized. Single crystal X-ray diffraction shows that Cu(II) in the two complexes has similar five-coordinate structure, including four nitrogens from two phen and one nitrogen from FOX-7 anion. Thermal decomposition behaviors of the two complexes were studied with differential scanning calorimetry and thermogravimetry/differential thermogravimetry methods. The apparent activation energies and pre-exponential constants of the main exothermic decomposition reaction for the two complexes are 208.1 and 183.1 kJ mol−1, 1022.99 and 1019.19 s−1, respectively. The self-accelerating decomposition temperature and critical temperature of thermal explosion for the two complexes are 152.64 and 162.17 °C, 161.50 and 173.29 °C, respectively.