NO₂ is a toxic gas that can react with other organic compounds in the air, causing air pollution and posing a significant harm to human health. Therefore, a gas sensor that can detect NO₂ is needed. However, conventional NO₂ gas sensors are difficult to operate at room temperature (25 ℃). In this work, NO₂ gas sensing based on SnS₂/In₂O₃, which can operate at room temperature (25 ℃), is reported. In₂O₃ quantum dots and SnS₂ nanosheets are prepared by the hot-injection method and hydrothermal method. By using the unique two-dimensional structure of SnS₂, In₂O₃ is decorated on it, and the composite enhances its sensing performance. The products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the composites prepared by 52% In₂O₃ exhibit the best sensing response. The fabricated sensor shows a response range from 26.6 to NO₂ of 1×10^–6 in volume fraction, fast response and short recovery time at room temperature (25 ℃). Moreover, this sensor demonstrates excellent reproducibility and selectivity. The heterojunction structure increases the number of active sites and accelerates the gas transport, which promotes charge transfer and gas desorption to improve NO₂ gas sensing performance. This excellent sensing performance has a great application prospect in NO₂ detection.