The single crystal of hydrazinium 3，5-dinitroamino-1，2，4-triazole （HDNAT） was cultivated by slow evaporation from solvent of methanol/water， and its crystal structure was determined by X-ray singal-crystal diffractometer. The crystal structure analysis indicates that HDNAT belongs to monoclinic system with space group P2（1）， and the crystal parameters are a = 0.35976（12） nm，b = 0.9348（3） nm，c = 1.1833（4） nm，V = 0.393.9（2） nm³，Z = 2，D_c = 1.91 g·cm^-3，μ = 0.170 mm^-1，F（000）=230. The thermal behavior of HDNAT was studied by TG-DTG. The decomposition peak of HDNAT is 193.17℃ （DSC）， and it decomposes at solid state. The composite modified double-base （CMDB） propellant formulation based on HDNAT was designed and prepared， and its energy characteristics such as explosion， specific volume， density， characteristic velocity， and specific impulse and combustion performances were tested. For HDNAT-based CMDB propellant formulation， the tested explosion is 6042 kJ·kg^-1， specific volume is 638 L·kg^-1， density is 1.767 g·cm^-3， characteristic velocity is 1592.3 m·s^-1. The study of combustion performances of Φ50 mm engine show that it has stable performances at pressure of 15 MPa， the specific impulse is 250.91 s. Compared with RDX-CMDB propellant， the burning rate of HDNAT-based CMDB propellant increases by 18.8%， and the pressure exponent in partial pressure range is above 0.4.