Carbon dioxide is one of the most important greenhouse gases playing an important role in climate change and human activities,so the detection of carbon dioxide concentration has an important significance.Highly sensitive detection of carbon dioxide gas was achieved by using near infrared tunable diode laser absorption spectroscopy combined with self-designed portable miniaturized cylindrical mirror multi-pass absorption cell.The cylindrical mirrors multi-pass absorption cell was optimized and designed by using a light transmission matrix programmed with Matlab software,compared with traditional Herriott multipass cell,which has the advantages of high mirror utilization and longer optical path length in the same volume.An effective optical path length of 14 mwas achieved with 15 cm physical length.In present work,a DFB diode laser emission at 1.57mum was used as a light source.Direct absorption spectroscopy method was used to detect the CO_2,and the Allan variance was used to analyze the system performance.The results showed that the detection sensitivity of the system can be achieved 5.3muL·L~(-1) with the average time of 5 s,and a detection sensitivity of 33.1muL·L~(-1) can be achieved by averaging in 235 s.In addition,CO_2 in the atmosphere was measured by the developed CO_2 sensor,the measured results showed that the concentration of CO_2 in the atmosphere is about 383.4muL·L~(-1).The tunable diode laser absorption spectroscopy(TDLAS)system based on cylindrical mirrors multi-pass absorption cell,combined with the cylindrical mirrors multi-pass cell can achieve long optical path in a small volume and tunable diode laser absorption spectroscopy technology has the advantages of high sensitivity,high resolution and fast response,greatly reduces volume and improves detection sensitivity of the system,which has a broad application in the field of gas detection.