Abstract: Due to high temperature coefficient of temperature (TCR), low noise level, and excellent CMOS process compatibility, vanadium oxide films are widely used as thermally sensitive layers in uncooled infrared bolometer detectors. To suppress the sunburn effect in uncooled infrared detectors under high-temperature fields of view, we optimized the detector fabrication process, enhanced substrate thermal treatment techniques, and studied their influence on the thermostability of vanadium oxide films. The results demonstrate that substrate thermal treatment can reduce the types and amounts of impurity bonds, improve the surface roughness of silicon nitride, and inhibit the crystallinity, stress, and resistivity deterioration of vanadium oxide films after thermal tolerance experiments. By comparing the time-dependent output differences between two detectors—with and without optimization—both subjected to prolonged high-temperature blackbody radiation, we conclude that substrate thermal treatment is beneficial for improving the thermostability of vanadium oxide and suppressing the sunburn effect in uncooled infrared detectors. This study provides a new direction for research on the reliability of uncooled infrared detectors.