High-nitrogen polycyclic frameworks， owing to their high nitrogen content and favorable oxygen balance， have attracted considerable attention as promising scaffolds for the development of novel high-energy energetic compounds. A novel high-nitrogen polycyclic nitramine energetic compound， 3-（4-nitropyrazol-1-yl）-7-（N-methylnitramino）-［1，2，4］triazolo［1，5-b］［1，2，4，5］tetrazine （compound 4）， was synthesized via a three-step reaction based on the ［1，2，4］triazolo［1，5-b］［1，2，4，5］tetrazine scaffold. The chemical structure of compound 4 was fully characterized by nuclear magnetic resonance spectroscopy （NMR）， high-resolution mass spectrometry （HRMS）， and infrared spectroscopy （IR）. Single crystals suitable for X-ray diffraction were obtained by slow solvent evaporation， and the crystal structure was determined by single-crystal X-ray diffraction. Results show that compound 4 crystallizes in the orthorhombic crystal system with the Pbca space group and exhibits a layered stacking structure with a room-temperature density of 1.701 g·cm^-3. Thermogravimetry-differential scanning calorimetry （TG-DSC） analysis reveals that the compound possesses a thermal decomposition temperature of 167 ℃. Calculations using the EXPLO5 software demonstrate that its theoretical detonation velocity and detonation pressure reach 8078 m·s^-1 and 25.2 GPa， respectively. Additionally， the impact and friction sensitivities of compound 4， determined by the BAM standard method， are 9 J and 180 N， respectively.