The geometrical structure of aluminum triazide was optimized at the B3LYP/6-311G^* level of theory. Its density, heat of sublimation and heat of formation of aluminum triazide were estimated theoretically, and explosion parameters was calculated and compared with TNT. According to the principle of zero oxygen balance, when it added into the composite explosive of AN and TNT, those parameters were predicted and compared with those of composite explosive containing the same quality of Al. The detonation heat, specific volume of explosion, detonation temperature, detonation velocity, detonation pressure and working capacity of aluminum triazide is 5170.20 kJ·kg^-1, 585.62 L·kg^-1, 5028.12 K, 9095.23 m·s^-1, 31.02 GPa, 1105.14 kJ·kg^-1respectively, indicating that its properties are better than those of TNT except detonation velocity and working capacity. Therefore it is a potential explosive compound. When the quality percentage of Al is 6%, the above parameters of the composite explosive of AN, TNT and aluminum triazide were 4351.49 kJ·kg^-1, 892.22 L·kg^-1, 3142.50 K, 8344.09 m·s^-1, 27.55 GPa, 1417.11 kJ·kg^-1 respectively. Aluminum triazide is a potential high-energy ignition agent，since it can improve the detonation heat, detonation temperature, detonation velocity, detonation pressure and working capacity of the composite explosive.