As motor vehicle exhaust emission causes more and more serious pollution in recent years, the natural environment and human health are facing great threats. It is of great significance to accurately measure the concentration of carbon monoxide, as one of the main pollutants of vehicle exhaust emissions. The detection system based on tunable diode laser absorption spectroscopy (TDLAS) is featured by high resolution, high sensitivity and fast response. Besides, TDLAS can eliminate the interference of the remaining gas by using tunable and narrow linewidth characteristics of semiconductor lasers, and selecting the single absorption line of specific gas, and finally realize the gas concentration inversion of high precision. Based on TDLAS, the motor vehicle exhaust component CO concentration detection system was designed and realized by using DFB laser with the center wavelength of 2330nm and selecting the absorption lines of CO gas at 2333nm. The hardware composition and software design of the system were introduced. In the experiment, motor vehicle exhaust of different vehicles was collected, and spectrum data obtained through the system components were used for CO concentration inversion. To improve the signal-to-noise ratio of the system and reduce the detection limit of the system, the balance detection technology was used in the system. Experiments show that the system has excellent stability, and can ensure accurate inversion of concentration results, and meet the real-time on-line detection of vehicle exhaust CO concentration.