Based on the density functional theory and using the first- principles plane- wave ultra- soft pseudopotential method, The models are set up for a pure InI and two different concentrations of Pb-doped In_1-xPb_xI(x=0.125,0.25). After the geometry optimization is finished, the band structures, the total electron density of states and absorption spectrum are calculated. The calculated results of the geometrical structure show that with the Pb doping consistence increase, the lattice constants change, the volume of lattice reduces, the energy of doping system decreases thereby making the structure more stable. Electronic structure calculation indicates that Fermi energy level enter into the conduction band, the doping system are high doped. Meanwhile in the doping system, the optical band gap increases, the electron effective mass decreases, the conductivity increases. Optical properties calculation indicates that the absorption spectrum of the doping system is blue-shifted, indicates that Pb doping makes the optical band gap of InI system increase. It shows that these results provide theoretical guidance for the experimental study of optical and electrical properties of doped InI material.