The potential of Sr-doped LaFeO3 as a nitrogen oxide–sensing material was studied by experimentation and theory calculation. The test results showed a much higher sensitivity and selectivity for a nitric oxide sensor based on Sr-doped LaFeO3 than on pure LaFeO3. The response, which was increased nearly 0.5-fold compared to pure LaFeO3, was attributed to an enhancement of oxygen vacancy and adsorbed oxygen. Further theoretical analysis indicated that Sr doping resulted in the formation of oxygen vacancy defects and altered the adsorption energy of the material, leading to an increase in chemisorbed oxygen species and intermolecular interactions. This work emphasizes the significance of oxygen vacancy defects in gas sensors and provides a feasible approach for enhancing the properties of gas sensors.