Abstract: With the intensification of greenhouse effect and global warming, the demand for carbon dioxide sensors is more urgent. Among carbon dioxide sensors, semiconductor gas sensors are the most common. The semiconductor gas sensor has low working temperature and high sensitivity, but the selectivity is not good. The selectivity of electrochemical gas sensor is greatly improved because its sensitive electrode has a specific catalytic effect on CO₂. Compared with traditional sensors, nano sensors can enrich the sensor theory from the micro point of view. The most common nano material is metal oxide. With the deepening of research, the performance of gas sensor is further improved by adding some noble metal catalysts to metal oxides and using visible light catalysis. This paper expounds the carbon dioxide gas sensor, and focuses on the principle, research progress and development trend of carbon dioxide gas sensor.