Single atom catalysts (SACs) have garnered significant attention in the field of catalysis over the past decade due to their exceptional atom utilization efficiency and distinct physical and chemical properties. For the semiconductor-based electrical gas sensor, the core is the catalysis process of target gas molecules on the sensitive materials. In this context, the SACs offer great potential for highly sensitive and selective gas sensing, however, only some of the bubbles come to the surface. To facilitate practical applications, we present a comprehensive review of the preparation strategies for SACs, with a focus on overcoming the challenges of aggregation and low loading. Extensive research efforts have been devoted to investigating the gas sensing mechanism, exploring sensitive materials, optimizing device structures, and refining signal post-processing techniques. Finally, the challenges and future perspectives on the SACs based gas sensing are presented.