Aluminum doped ZnO (AZO) thin films doped has been prepared by thermal evaporation method onto glass substrates. The optical characterization has been studied by UV-Visible Spectrophotometer in the range (300-1100) nm. The transmittance increased with increasing Al-doping, while absorption decreases with increasing Al-doping content. The energy gap (Eg) values increased with increasing Al-doped in the ZnO:Al thin films. The refractive index, extinction coefficient, and real and imaginary dielectric constants obtained results show that doping content strongly affects the optical parameters of AZO thin films. Optical constants tend to decrease with increasing doping content.