Transparent and conductive oxides CdIn2O4 (CIO) thin films were prepared by RF reactive sputtering from a CdIn alloy target in Ar+O2 atmosphere. By the analysis and measurements of transmittance spectra and Hall_effect of different samples prepared at different substrate temperatures and post_deposition annealing in an Ar gas flow, it was found that the carrier density increases with the d ecrease of substrate temperature, but the absorption edge shows an abrupt change from a blue_shift to a red_shift. Theoretically, the paper formulated the effec t on band structure due to higher density of point defects, it embodies the band _tailing, Burstein_Moss (B_M) shift and band_gap narrowing. In addition,density of ionized impurity substrate temperature induced will affect the carrier mobili ty.The hole density impurity_induced will influences the magnitude of optical ba nd_gap and transmittance of light. Since extrapolation method does not fit degen erate materials, a more accurate method of obtaining band_gap is the method of c urve fitting.