2,2,6,6-Tetranitroadamantane was synthesized by direct oxidative nitration from adamantane-2,6-dionedioxime, which was prepared via oxidation and oximation of adamantane. The structures of the products were confirmed by ¹H NMR, ¹³C NMR, IR and elementary analysis. The reaction conditions of the oxidative nitrition were optimized as following: n(adamantane-2,6-dionedioxime):n(dinitrogen pentoxide)=1:6, reaction solvent CH₂Cl₂, reaction temperature 50 ℃ and reaction time 30 min, with the yield of 50%. The thermal properties of 2,2,6,6-tetranitroadamantane were analyzed by thermogravimetry (TG) and differential scanning calorimetric (DSC) measurements. Results show that its decomposition temperature is 275 ℃ and exothermic peak temperature is 298 ℃, which indicate that 2,2,6,6-tetranitroadamantane has good thermal stability.