MgxZn1-xO films(x=0.16) have been prepared at 80℃ by radio frequency magnetron sputtering. The effect of the annealing temperature on the structure and optical properties of the films are studied using XRD, photoluminescence and the transmittance spectra. The results indicate that the thin films have hexagonal wurtzite single phase structure and a prefered orientation with the c axis perpendicular to the substrate. With increasing annealing temperature the intensities of the XRD (002) peaks increase, the grain size and intensity of the UV photoluminescence peaks also increase, while the FWHM of (002) peaks decreases, which demonstrates that high quality MgxZn1-xO films deposited by RF magnetron sputtering can be obtained by properly controlling the annealing temperature.