A near-infrared laser carbon dioxide (CO₂) sensor system is developed using tunable diode laser absorption spectroscopy (TDLAS). The system consists of a distributed feedback laser with a central wavelength of 1572 nm, a dense spot-type gas chamber, and an indium gallium arsenic detector. LabVIEW program is used to extract the amplitude of the second harmonic signal and the CO₂ concentration is inverted. In order to characterize the sensor performance, gas detection experiments are carried out by using the system. The results show that,when the modulation depth is 0.32 cm ^-1, the amplitude of the extracted second harmonic signal is the largest. In the volume fraction range of 0-3%, the amplitude of the second harmonic signal has a high linearity with the CO₂ concentration (the goodness of fit is 0.999). When the volume fraction of CO₂ is 0, the retrieved concentration fluctuation range is -2×10 ^-4-1.17×10 ^-4 after continuous test for 1 h. When the integral time is 297 s, the lower limit of sensitivity detection of the system is 2.7×10 ^-6. Considering the gas diffusion time during dynamic gas distribution, the response time of the system is 40-42 s. The CO₂ concentration in the atmosphere is measured continuously for 15 h, and the average CO₂ volume fraction measured is about (560±46)×10 ^-6. Compared with the reported sensors, the gas sensing system presents similar quality factors and can be popularized and applied in industrial and agricultural production, environmental protection and other fields.