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波长调制谱技术(WMS)在慢扫描信号基础上叠加上高频的调制电流，并加到半导体激光器的驱动电流上，于是激光频率在线性扫描的同时受交流调制。频率调制的激光束在通过吸收气体以后，其吸收线的强度也受到相同频率调制。采用谐波小波方法作为数据解调的手段，对WMS技术产生的信号进行处理并实现了2 f信号的提取。采用这种方法对波数为7185.6 cm-1的水蒸气谱线进行测量实验，调制频率达到180 kHz，对数据进行谐波小波处理后获得了高质量的2f信号，该2f信号的峰值中心辨识度高，其数据光滑度、信号的抗干扰能力方面均优于数字锁相方法。“,”Wavelength modulation spectroscopy (WMS) technique uses high- frequency modulation signal which is superimposed on the slow scanning signal. The signal is applied to the semiconductor laser drive current, so the laser frequency linear sweep as well as the modulation sweep. The absorption intensity of the lines is also modulated by the same frequency. 2f signal extraction of WMS was achieved by harmonic wavelet, which is the tool for data demodulation. The absorption spectroscopy data was obtained by scanning the beams from a tunable diode laser operating near the 7 185.6 cm-1 with the modulation frequency of 180 kHz. The 2f signal of high quality was obtained after harmonic wavelet processing for the data. The 2f signal’s identification of its peak center is very clear, and data smoothness, anti-interference ability of the signal is better than method of digital lock- in.