In-doped ZnO thin film has been found as one of the most promising materials in the optoelectronics, but its optical properties are rarely reported. We calculated optical band gaps and optical properties of Zn1-xInxO with different In doping by using first-principle. The results reveal that the lattice constants of Zn1-xInxO increase linearly with the doping increasing and Zn1-xInxO (x=0.125, x=0.25) crystal comes to be degenerate semiconductor with band gap reduced. The imaginary part of dielectric function has an increasing trend and the absorption capacity significantly increases in ultraviolet (UV) range after doping. Also there is an obvious red-shift in the absorption spectrum. The reflectivity and energy loss spectrum were investigated, too. The results can provide a theoretical reference for finding appropriate UV protective material.