The ultrasonic spray pyrolysis was used on quartz glass substrate unde r the fixed conditions which are substrate temperature of 440℃,distance from nozzle to substrate of 4cm,doped Zn∶Mg∶Sn of 97.6∶2∶0.4and carrier gas flow of 0.8L/min.Sn-Mg co-doped ZnO films with differen t deposition time of 5min,7min,9min and 11min were prepared.The film structure and surface morphology,luminescence properties,tra nsmittance,the film thickness and electrical properties of the films were characterized by X-ray di ffraction (XRD),scanning electron microscope (SEM), photoluminescence (PL),ultraviolet visible (UV-VIS) spectrophotometer,film thickness (SCG-10) and current-voltage (I-V) curves.W hen the deposition time is 7min,XRD pattern shows that the peak intensity of (101) film is maximum, and the preferred orientation of the growth is obvious.The SEM diagram shows that the surface of the film is dense and smooth,the particles ar e uniform,the size is the largest,and the shape is the best.The emission peak intensity is the largest,an d the peak shape is the sharpest at 372nm.The transmittance of all films is over 80% in the visible region,which shows excellent light transmission.By comparing and calculating with the change of the band gap value, the results show that when the deposition time is 7min,the band gap value of the film is maximu m.According to the I-V characteristic curve of the film,the resistance is the smallest,and the conduct ivity is the best.