We have employed ab-initio plane-wave pseudopotential density functional theory to calculate the equilibrium lattice parameters, elastic constants, under the hydrostatic pressures from 0 to 100 GPa for P1-IrB with Pnma space group and P5-IrB2with Pmmn structures. Results show that the P1-IrB structure is stable, and the incompressibility is enhanced with the increase of pressure. And the elastic constants, bulk modulus, shear modulus for P5-IrB2structure exhibit the regular changes under the hydrostatic pre...