在基于可调谐二极管激光吸收光谱技术（TDLAS）红外气体检测系统中，用来表征气体体积分数大小的二次谐波信号，易受到各类硬件参数的影响。基于比尔朗伯定律与HITRAN数据库，使用LabVIEW研究参数对二次谐波的谐波幅值、对称度、峰宽的影响，并进行了谐波优化仿真实验。结果表明：对于一般TDLAS检测系统，应优先选择合适的扫描幅度与滤波器阶数，使得谐波波形完整且不失真；然后尽可能增大谐波幅值与峰宽，得出最佳调制度；最后根据系统需求和自身硬件基础，选择合适的调制频率与扫描频率。

In the infrared gas detection system based on tunable diode laser absorption spectroscopy (TDLAS), the second harmonic signal is used to calculate the gas percentage by volume. However, this signal is easily influenced by many parameters of the hardware. Based on Lambert Beers law and HITRAN database, this paper used LabVIEW to study the influence of parameters on the amplitude, symmetry and peak width of the second harmonic, and carried out the harmonic optimization simulation experiment. The results show that, for the general TDLAS detection system, the appropriate scanning amplitude and filter order should be chosen firstly, so that the harmonic line would be complete and undistorted. Furthermore, the amplitude and peak width of the harmonic should be increased as much as possible to get the optimal modulation depth. Finally, the suitable modulation and scan frequency should be determined choose according to the system requirements and the hardware conditions.