Herein, we report a two-step low-temperature annealing method to enhance performance of InSnO (ITO) thin-film transistors (TFTs). In case of one-step annealing treatment, threshold voltage (V_th) of the ITO TFTs present a negative correlation with annealing temperature. Therefore, we design a two-step low-temperature annealing process to purposely modulate electrical properties of the ITO TFTs. The results show that the ITO TFTs annealed at 200 °C for 1 h at first and then annealed at 150 °C for 0.5 h exhibit the best performance, and the major properties includes a saturation mobility (µ_sat) of 21.0 cm²V^-1s^-1, a V_th of -1.1 V, a subthreshold swing (SS) of 560.5 mV/cm, and an on-to-off state current ratio (I_on/I_off) of 5.79 × 10⁸. Moreover, the ITO TFTs exhibit excellent bias stress stability. This work demonstrates a low-temperature approach for the enhancement of the oxide TFTs.