SnO₂ has been extensively used in the detection of various gases. As a gas sensing material, SnO₂ has excellent physical-chemical properties, high reliability, and short adsorption-desorption time. The application of the traditional SnO₂ gas sensor is limited due to its higher work-temperature, low gas response, and poor selectivity. Nanomaterials can significantly impact gas-sensitive properties due to the quantum size, surface, and small size effects of nanomaterials. By applying nanotechnology to the preparation of SnO₂, the SnO₂ nanomaterial-based sensors could show better performance, which greatly expands the application of SnO₂ gas sensors. In this review, the preparation method of the SnO₂ nanostructure, the types of gas detected, and the improvements of SnO₂ gas-sensing performances via elemental modification are introduced as well as the future development of SnO₂ is discussed.