Five new high-pressure phases ( I 4̄3 d -Y 4 N 3 , R 3 c -Y 2 N 3 , P 1̄-II-YN 4 , P 1̄-YN 6 , and P 31 c -YN 8 ) are proposed by the crystal structure prediction. A series of polynitrogen forms were achieved in the nitrogen-rich Y-N compounds, including diatomic N 2 , an isolated N 8 chain, an infinite N chain with an N 6 unit, and an infinite N layer with bent N 18 rings. The high energy densities of P 1̄-II-YN 4 (1.98 kJ g -1 ), P 1̄-YN 6 (2.35 kJ g -1 ), and P 31 c -YN 8 (3.77 kJ g -1 ) make them potential high energy density materials. More importantly, P 1̄-II-YN 4 , P 1̄-YN 6 , and P 31 c -YN 8 exhibit excellent explosive performance, with detonation pressures 4-8 times that of TNT (19 GPa) and detonation velocities 1-2 times that of TNT (6.90 km s -1 ). The electronic structure and bonding properties show that the high stability of Y-N compounds originates from the strong N-N covalent bond and the weak Y-N ionic bond interaction. The increase in the transferred charge quantity as the pressure decreased is more conducive to stabilizing the polymeric nitrogen structure, which leads to the metastable properties of P 1̄-II-YN 4 and P 1̄-YN 6 under ambient conditions. Finally, the infrared (IR) spectra of P 1̄-II-YN 4 , P 1̄-YN 6 , and P 31 c -YN 8 are calculated to provide a reference in experimental synthesis.