N,N"-Bis(fluorodinitroethyl)-3,4-diamino furazan (LLM-208) was nitrated using the nitration system of 98% fuming nitric acid/acetic anhydride (10∶8 in volume) at 0 ℃. N,N′-bis(2-fluoro-2,2′-dinitroethyl)-3,4-dinitraminefurazan (LLM-209) was prepared from LLM-208. The single crystal of LLM-209 was obtained by volatilization culture in anhydrous methanol. The single crystal structure was measured by X-ray single crystal diffractometer. The thermal decomposition of LLM-209 was studied by thermogravimetry and differential scanning calorimeter（TG-DSC）. The gaseous products of thermal decomposition of LLM-209 were measured by TG-IR. The detonation velocity and detonation presure of LLM-209 were predicted by EXPLO5(V6.02) program. Its impact and friction sensitivities were measured by sensitivity test.Results show that the crystal of LLM-209 belongs to the monoclinic system, space group P2₁/n, and its density at 298 K is 1.94 g·cm^-3. LLM-209 has a melting endothermic peak at 94.27 ℃ and two distinct decomposition exothermic peaks at 179.96 ℃ and 233.86 ℃. The gaseous products of thermal decomposition of LLM-209 are mainly NO₂，CO₂，CO and N₂O. The theoretical detonation velocity and detonation presure of LLM-209 are 8981 km·s^-1 and 40.3 GPa, respectively, and the impact and friction sensitivities are 4 J and 48 N, respectively.