We present density functionary theory (DFT) calculations on the structural parameters and electronic structure for iridium nitride by using the generalized gradient approximation (GGA) and the Perdew-BurkeErnserhof (PBE) exchange-correlation functional. The lattice parameters and bulk modulus (B 0 ) for the ground state are obtained, and the energy band structure and electron densities of states (DOS) of IrN 2 are presented. It is found that IrN 2 has a very close indirect energy gap. There is a strong covalent bond between the two nearest N atoms. This gives rise to a very high elastic modulus of IrN 2 and reveals the quasimolecular nature of the N 2 in IrN 2 crystal. Lattice parameters, bulk modulus, and the electronic structure of IrN 2 under high pressure have also been investigated based on DFT. The compressibility along three cell vectors is very close to each other. The band gap increases a little with the pressure even when the pressure is up to 100 Gpa.