采用波长2μm附近的可调谐半导体激光二极管作为光源,结合多步吸收光程和光纤传输技术,通过激光吸收光谱直接测量方法对CO2分子浓度进行测量研究。实验在标定了激光器调谐范围内17条CO2吸收谱线的波长及相应的吸收带跃迁的基础上,研究了不同压力下纯CO2气体在2008nm附近的吸收光谱,由吸收信号随气体压力的变化关系得到低气压下实验装置的系统刻度因子。并进一步对样品气体的CO2浓度进行测量,测量给出CO2分子浓度为(2.754±0.145)×1016 cm-3,测量误差主要来源于目前实验中所使用的气压计的精度和读数局限性。该研究为气体分子浓度测量、同位素含量分析提供了一种光谱测量方法。 The tunable semiconductor laser diode with a wavelength of 2μm was used as the light source, and the multi-step absorption optical path and optical fiber transmission technology were used to measure the concentration of CO2 molecules by direct laser absorption spectroscopy. Based on the calibration of the wavelength and the corresponding absorption band transition of 17 absorption lines in the tuning range of the laser, the absorption spectra of pure CO2 gas at around 2008 nm under different pressures were studied. The absorption spectra were related to the gas pressure The system scale factor of the experimental device under low pressure was obtained. And further measure the CO2 concentration of the sample gas. The CO2 molecular concentration is given as (2.754 ± 0.145) × 1016 cm-3. The measurement error comes mainly from the accuracy and reading limitation of the barometer used in the present experiment. This study provides a spectrometric method for gas molecule concentration measurement and isotope analysis.