Doping transition metal or rare-earth metal ion are one of the most popular topics in semiconductors. In this work, gadolinium (Gd) doped zinc oxide thin films was prepared using spin-coating technique with different concentrations in atomic percent (at.%). The influences of rare-earth ions doped into the zinc oxide films were studies. The effects on the physical and optical properties of the films were investigated by field emission scanning electron microscope, x-ray diffraction, atomic force microscopic and ultraviolet-visible spectrophotometer. It was found that the properties of zinc oxide can be tuned by changing the concentration physical and optical of Gd.