Indium-zinc oxide (IZO), with Zn/(Zn+In)=0.33 - 0.78, films were deposited by the sol-gel method. Effects of Zn/(Zn+In) atomic ratio and annealing temperature on the structural, electrical and optical properties of IZO thin film were investigated. Films of Zn/(Zn+In)=0.33 prepared at 600°C had the lowest resistivity value, 4.48X10 -2 Ω cm (carrier concentration=3.83X 1018 cm-3 and mobility=25.54 cm2/Vs), and the structure of these films matched that of Zn2In2O5 film. Average optical transmittances of all films were above 80% in the visible range. The highest average transmittance was observed at Zn/(Zn+In)=0.5, with 86.8% in the visible range.