In this work we have used density-functional theory methods such as full-potential local orbital minimum basis（FPLO） and ELK-flapw to study the electronic structure of newly discovered Laves phase superconductor CaIr_2.The calculation of density of states（DOS） indicates that the bands near Fermi level are mostly occupied by the d-electrons of iridium.The simulation of de Haas-van Alphen（dHvA） effect has been performed by using Elk code to check the Fermi surface topology.The results show that there exist four Fermi surfaces in CaIr_2,including two electron-type and two hole-type surfaces.The optical response properties of CaIr_2 have been calculated in the dipole-transition approximations combined with including intra-band Drude-like terms.In the optical spectrum σ（ω） shows that the crossover from intraband to inter-band absorption occur near 1.45 eV.Further analysis on the electron energy loss spectra（EELS） matches the conclusion from that of optical conductivity σ（ω）.
