22 Tetrazine substituted by six-membered C—N heterocyclic derivatives have been investigated by density functional theory. Their optimized geometry structures, electronic structures, conjugation, molecular energies, heats of formation (HOF) and density (ρ) were calculated at the B3LYP/6-311G(d,p) level. The results show that most of the species keep a planar structure and exit considerable conjugation over the whole molecule, which enhances the stability of these derivatives. There is a good linear relationship between the molecular energies, density and N atoms in these species. The studies show most of the species have high HOFs and relative stabilities. The HOFs of these compounds are between 631.1 kJ·mol^-1 and 1465.6 kJ·mol^-1.