In this study, gallium tin oxide (GTO) thin-film transistors (TFTs) are fabricated by ultrasonic spray pyrolysis deposition (USPD) method, which has considerable advantages in process time and cost. The GTO TFT exhibits the on/off current ratio of ~10⁹, subthreshold swing (SS) of 133.08 mV/dec, the field-effect mobility (μ_FE) of 33.79 cm²/V-s, the threshold voltage (V_th) of 0.41 V and the V_th shift under the 3000-seconds NBIS is -0.24 V by optimizing the Ga/Sn atomic ratio.