1, 2-Dinitroguanidine(DNG) was synthesized via the nitration reaction using nitroguanidine(NQ) as raw material and 100% nitric acid/20% oleum/ammonium nitrate as nitrating system. The structure of DNG were identified by IR, ¹H NMR, ¹³C NMR and MS. The factors affecting the yield of DNG and orthogonal experiment were investigated. The thermal decomposition behavior of DNG was studied using TG and DSC. The results show that the optimized conditions of the nitration reaction are: n(HNO₃):n(NQ):n(NH₄NO₃)=15:2:1, V(H₂SO₄):V(HNO₃)=1.25:1, the reaction time 8 h and reaction temperature 10 ℃. The yield of DNG can reach up to 61.76% under the optimized conditions. The peak temperature of DSC curve for DNG is 182.83 ℃, indicating that DNG has a better thermal stability.