To address the problem of low detection accuracy in the traditional method of seed-breathing CO2 concentration measurement, a seed-breathing measurement system based on tunable diode laser absorption spectroscopic technology was proposed to meet the needs of seed-breathing CO2 concentration measurements. First, the system was designed to consist of a seed-breathing container, a distributed feedback laser and control circuit, photoelectric conversion and an amplification circuit, a data acquisition circuit, and upper computer software. The space volume of the seed breathing container was 1.5 L, the laser source was in the 2 004-nm band, and the light path of the multiple reflection cell was 16 m. Then, based on Lamberts law and wavelength modulated absorption spectroscopy, the concentration of CO2 produced during seed respiration could be retrieved in real time using second harmonics. The stable repeatability of the CO2 concentration measurement in seed respiration is 0.033%, the linear fitting degree of CO2 concentration is 0.999 38, and the detection limit of CO2 concentration is 1.7×10-6. The change curve of 20-g maize seed respiration is obtained by testing waxy maize seeds. The amount of change in waxy maize seed respiration after 12 h is 2 750.5×10-6, and the respiration rate is 229.2×10-6/h. Experimental results show that the system can solve the inability for continuous measurement of CO2 concentration in seed respiration and the low precision of concentration detection.