Glycocluril (GU) was prepared in the presence of hydrochloric acid by microwave heating with urea and glyoxal as raw materials. Through fuming nitric acid and acetic anhydride, tetranitroglycoluril (TNGU) was synthesized from nitration of GU. The effects of reaction temperature, reaction time and dosage of fuming nitric acid on the nitration were investigated. The structure of TNGU was characterized by IR, ¹H NMR, ¹³C NMR and elemental analysis. Thermal analysis of TNGU was studied by DSC, and thermal decomposition kinetics parameters such as E_K, A and E_o were respectively calculated with Kissinger and Ozawa, and E_K and E_o were significantly consistent. The critical temperature of thermal explosion (T_b), the entropy of activation (ΔS^≠), enthalpy of activation (ΔH^≠) and free energy of activation (ΔG^≠) of thermal decomposition were calculated. Results show that the optimal technological conditions for synthesizing TNGU were as follows: urea 5 g, fuming nitric acid 70 mL and acetic anhydride 35 mL, reaction temperature between 25~30 ℃, reaction time 4 h, the yield of tetranitroglycoluril was 84% (according to GU). Under these conditions, the amount of waste acid was 30 mL, less than that in literature, and nitration time was shortened by 4hs. T_b of TNGU is 465.34 K, and its ΔS^≠, ΔH^≠ and ΔG^≠ are 171.46 J·mol^-1, 195.00 kJ·mol^-1 and 194.99kJ·mol^-1 respectively. The thermal decomposition of TNGU was exothermic with increasing entropy.