甲烷是天然气和矿井瓦斯等多种气体燃料的主要成分，由于其易燃易爆的特性，瓦斯爆炸一直困扰着天然气站和煤矿的安全生产。可调谐半导体激光光谱(TDLAS)技术是近年来发展起来的一种新型的气体检测方法。它具有灵敏度高、精度高、选择性强、响应快速等突出特点。波长调制光谱(WMS)技术是TDLAS技术中一种重要技术。利用WMS技术检测在大气压下、浓度从0．04%至10%的甲烷气体的二次谐波(2f)信号，并证明了在该浓度范围内2f信号幅值正比于甲烷的浓度，为工业中甲烷气体的浓度监测提供了一种新的检测方法，并为集成甲烷监测仪器提供了理论及实验的依据。

Methane is a major constituent of natural gas,mine atmospheres,and gas fuels.On account of its inflammable and explosive characteristic,gas explosion is a big problem in natural gas station and mining industry. Tunable diode laser absorption spectroscopy(TDLAS)is a gas detection technique provided with high sensitivity,high precision,high selectivity,and rapid responsibility,which has large development in recent years. Wavelength modulation spectroscopy(WMS)is an important technique of TDLAS. In this paper,the WMS technique have been used to detect the methane,and prove the intensity of 2f signals is in direct proportion to the methane concentration in the concentration range between 0.04% and 10%. This WMS technique can be used in methane detection in industrial occasion,and based on these an instrument of methane detection can easily be integrated.