Abstract: Methanol gas is toxic gas that can harm the human nerve system and blood circulation system. Developing devices capable of detecting methanol gas is of great significance. The use of sensors to detect methanol gas has the advantages of low cost, high sensitivity, and real-time monitoring. However, the mainstream methanol gas sensors mainly rely on metal oxides, which have the drawback of high operating temperatures. Therefore, we synthesized perovskite quantum dots CsPbBr₃ through a simple solution synthesis method, and passivated their surface defects using an acetylacetone indium ligand (In(Acac)₃), obtaining a material with good gas sensitivity to methanol gas at room temperature. The sensitivity to a volume fraction of 80×10^–6 methanol gas at room temperature is 0.25, and the response/recovery time is 11.0 s/17.0 s, gas sensitivity is further improved under ultraviolet light irradiation. It also has good reproducibility and stability, the sensitivity of the sensor has been maintained at around 0.25 after multiple tests at a volume fraction of 80×10^–6 methanol gas, and the sensor sensitivity has remained at a high level for 15 days. At the same time, it still has a good response to methanol gas under harsh conditions such as high humidity and no light. Considering that the structure of metal halide perovskite can easily adjust its properties by changing elements, this research method and experimental process can be applied to the detection of other gases.