Considering the advancement of contemporary industrialization and urban development, a consequential escalation of air quality deterioration has led to the emergence of diseases and disasters. In this research, we endeavor to harness the properties of MgNiO for the fabrication of a gas sensor designed specifically for the detection of NO2. In contrast to conventional NiO gas sensors, our findings indicate a noticeable enhancement in the sensor’s NO2 gas responsiveness with increasing proportion of Mg. Remarkably, the utilization of a Mg0.5Ni0.5O film exhibits the most promising outcomes, that is , heightened responsiveness and commendable selectivity. This improvement of performance can be attributed to the increase in oxygen vacancies within the film and consequent alterations in film resistance, which collectively contribute to the overall improvement of sensor responsivity.