With 1.3-diaminoguanidine hydrochloride and oxalic acid as starting materials, an insensitive energetic salt of 5,5′-diamino-4,4′-dinitroamino-3,3′-bi-1,2,4-triazole triaminoguanidinium salt (TAGAT) was synthesized by cyclization, nitration and salt formation reactions. The single crystal sample of TAGAT was obtained from water by cooling method and the detailed crystal structure was characterized by X-ray diffraction analysis. Results showed that TAGAT crystallizes in the monoclinic space group P2₁/c with cell parameters of a=11.4979(5) Å, b=6.3468(2) Å, c=14.0945(5) Å, β=101.7910(10)°, V=1006.84(6) ų, Z=2, µ=0.136 mm^-1, F(000)=516.0 and its crystal density was 1.631 g·cm^-3 at 170 K. Thermal behaviors of TAGAT were investigated through TG-DSC method, indicating an onset decomposition temperature of 211 ℃. Constant-volume combustion experiment showed that the maximum gas-generating pressure of TAGAT was 6.38 MPa and the average pressure-up rates of TAGAT was 0.275 GPa·ms^-1. Based on Born-Harber Energy Cycle, the Gaussian 09 program was applied to calculate the standard generation enthalpy of TAGAT as 1218.5 kJ·mol^-1. The detonation parameters of TAGAT were calculated with the EXPLO5(V6.02) program, leading to a calculated detonation velocity of 8795 m·s^-1, a calculated detonation pressure of 28.4 GPa and a calculated gas volume of 924.9 L·kg^-1. Sensitivities toward impact and friction were determined through BAM sensitivity testers, exhibiting that the impact sensitivity of TAGAT was 32 J and the friction sensitivity of TAGAT was greater than 360 N.