The geometry and the potential curve of thermal decomposition for 1,1′dimethyl-5,5′-azotetraol (1-DMAT) are calculated by ab initio quantum chemistry method. The structural characteristics and decomposition mechanism are carefully studied. It is found that the terrazzo ring satisfies 4n+2 rule and it is a conjugated π-system for 1-DMAT. The azotetrazol has aromatic characteristic and its thermal decomposition can proceed in two steps: ring opening and separation N2. The activation energies of the two steps are 243.5kJ/mol and 64.01kJ/mol, respectively. The ring opening is the rate-controlling step. The geometry and the potential curve of thermal decomposition for 1,1’dimethyl-5,5’-azotetraol (1-DMAT) are calculated by ab initio quantum chemistry method. The structural characteristics and decomposition mechanism are carefully studied. It is found that the terrazzo ring satisfies 4n + 2 rule and it is a conjugated π-system for 1-DMAT. The azotetrazol has aromatic characteristic and its thermal decomposition can proceed in two steps: ring opening and separation N2. The activation energies of the two steps are 243.5 kJ / mol and 64.01 kJ / mol, respectively. The ring opening is the rate-controlling step.