Ga-doped ZnO(GZO) films with low resistivity and high transmittance are got firstly on the condition that the thickness of films is smaller than 200 nm by RF magnetron sputtering. The microstructures of GZO films were observed with Scanning Electron Microscope(SEM). The optical and electrical properties of GZO films were respectively measured using a four-point probe technique and UV-2102 spectrophotometer. The results show that the resistivity of GZO films which decreased from 46.6×10-2.·cm to 2.5×10-2.·cm decreased rapidly with the sputtering power increasing. When the wavelength range was in 300~350 nm, the increase of sputtering power made the transmittance of GZO films decrease, but the width of transmittance increase. When the wavelength range was in 350~380 nm, the transmittance of GZO films was enhanced. The average transmittance of GZO films are more than 89%. With increasing of sputtering power, the bandgap of GZO films first increases, and then decreases. The surface morphology variation of GZO films show that the morphology of thin film changes from the apparent separation of particles to continuous distribution.