Ge doped ZnO films were synthesized on silicon substrate via RF magnetron co-sputtering methods. The effects of annealing temperature on the optical and structural properties of the Ge doped ZnO films were investigated by means of photoluminescence spectra, X-ray diffraction, and X-ray Photoelectron Spectroscopy. The ultra-violet emission should be related with the free-exciton recombination, and blue and yellow emissions should be attributed to the defect state caused by Ge. The varieties of annealing temperature affect greatly the optical properties. The high annealing temperature leads to the oxidation of Ge and the formation of Zn2GeO4, which could lead to the change of PL spectra.