To find the relationship between the structures and thermochemical properties of energetic compounds, the structures and thermochemical properties of 15 kinds of azo-bridged azoles were studied by density functional theory. Their structures were optimized at B3LYP/6-311+G (d, p) level, their entropies and constant-pressure specific heat capacity were calculated and their enthalpies of formation were estimated via design of the isodesmic reaction. Results show that the N atom and C atom on the heterocyclic ring are sp² heterocyclic atoms. All heterocyclic rings are nearly in the same plane. The enthalpy of formation of the compound is proportional to the number of nitrogen atom. For compounds with the same number of nitrogen atoms, the enthalpy of formation of the compound decreases with increasing the distances from the azo-bridge to nitrogen atom on heterocyclic ring and the distances between the nitrogen atoms on heterocyclic ring. The constant pressure specific heat capacity at different temperatures are inversely proportional to the nitrogen content (the number of nitrogen atom on the heterocyclic ring).