The polynitro imidazole derivative 1,5-dinitro-2,6-bis(trinitromethyl)-3a,4a,7a,8a-tetrahydro-[1,4]dioxino[2,3-d:5,6-d]diimidazole (DNTNDI) was synthesized through nitration of 2-(dinitromethylene)-1H-imidazol-4-ol in HNO3/Ac2O followed by cyclization of the di-enol. It was characterized by NMR, IR, elemental analysis, and single-crystal X-ray diffraction analysis. Compound DNTNDI crystallizes in the orthorhombic space group P2(1)2(1)2(1). The thermal decomposition was studied with thermogravimetry/derivative thermogravimetry (TG/DTG) in a nitrogen atmosphere with a heating rate of 5Kmin(-1). The TG/DTG analysis indicated that DNTNDI has 97.64% mass loss between 127 degrees C and 173 degrees C by undergoing exothermic decomposition. The density of DNTNDI was determined as 1.906gcm(-3) at 293K with an Ultrapycno 1000 Pycnometer. The denotation velocity and denotation pressure of DNTNDI were calculated as 9325ms(-1) and 40GPa by applying the LOTUSES (version 1.4) code, respectively. The oxygen balance of DNTNDI is 0 and its oxygen content amounts to 51.78%, which is superior to that of new generation of chlorine-free oxidizer ammonium dinitramide (ADN).