Li-doped ZnO films were prepared on Corning 1737 glass substrate by an rf magnetron sputtering technique using ZnO targets with various $Li_2CO_3$ contents ranging from 0 to 10 mol%. The effects of Li doping on the crystallinity and electrical properties of ZnO films were studied for their SAW filter applications. The film resistivity largely increased without suppressing the c-axis orientation and crystallinity with a small addition of Li. Heat treatment of the film at 40$0^{circ}C$ induced that the film resistivity, c-axis orientation and crystallinity slightly increased. However, heat treatment of the film at 50$0^{circ}C$ resulted in much lower resistivity than that of as-deposited film due to the increase of electron concentration caused by the evaporationof Li atoms from the ZnO film. Large addition of Li into the ZnO film rather diminished the film resistivity and suppressed the c-axis growth. It was concluded that a small doping of Li into the ZnO film and heat treatment at 40$0^{circ}C$ caused the film resistivity to be high enough for SAW filter applications without suppression of the c-axis orientation and crystallinity.