The thermodynamic parameters and the excited states of radiolysis products of 1, 3, 5-triamino-2, 4, 6-trinitrobenzene(TATB) were obtained by density functional theory calculation(DFT). The formation of benzoxadiazol-containing radiolysis products of TATB was found to be a thermodynamically spontaneous process, and the red shift of ultraviolet spectrum for benzoxadiazol-containing radiolysis products was confirmed through excited state calculation. The gamma-ray radiolysis products of TATB were studied by high-resolution electrospray ionization mass spectrometry(ESI-MS). Benzoxadiazol-containing radiolysis products of TATB were identified, which lead to the colour change of TATB. Calculated and experimental results revealed that benzoxadiazol-containing compounds were the main radiolysis products of TATB and a new endothermic peak in 600-700 nm, the reason of TATB colour change.