In order to understand comprehensively the thermal decomposition behavior of dihydrazinium salts of bis(5-amino- 1, 2, 3, 4-tetrazolium) (Hy₂BTA), thermal decomposition curves at different heating rates and the types of decomposition gas products and their content change of the compound were measured by combined method of thermogravimetry-differential scanning calorimetry-Fourier transform infrared spectroscopy-mass spectrometry (TG-DSC-FTIR-MS). Results show that the thermal decomposition of Hy₂BTA includes two endothermic processes and two successive exothermic processes with temperature increasing, corresponding to the broken of first ionic bond in Hy₂BTA with the expulsion of NH₂NH₂, the tetrazole rings began to release N₂ with the rupture of —N—N— during the break of the second ionic bond in Hy₂BTA, gas products N₂, HN₃, NH₃ and HCN were generated by the cleavage of tetrazole rings and the further decomposition of residual skeleton, in addition, the polymerization of decomposition products and pyrolysis of residual skeleton can be occurred which produce polymer containing nitrogen and HN₃, N₂ and NH₃, respectively. The apparent activation energies of four processes calculated by Kissinger′s method are 115.12 kJ·mol^-1, 193.75 kJ·mol^-1, 334.16 kJ·mol^-1 and 243.40 kJ·mol^-1 respectively.