Abstract: In order to real-time detect the main component of volatile organic compounds of oil gas and realize production safety in petrochemical industry, laser spectrum analysis technique was applied. Firstly, the broadband optical source was utilized to analyze the spectral absorption features of propane between 1686.00nm and 1687.00nm. The relationship between absorption coefficient and wavelength was fit into Lorentz lineshape, with half width at half max of 0.21nm. A distributed feedback laser with center wavelength of 1686.30nm was chosen as the sigle mode light source, and laser wavelength scan was made within wide absorption spectrum of propane. The changing regularity of the first and second harmonic signal with volume fraction of propane was acquired. The linear relationship between the ratio of the second harmonic signal to the first harmonic signal and propane volume fraction was calibrated with propane volume fraction from 0.0050 to 0.0300. The results show that, the system has good stability and repeatability, and can be used to do propane online detection. The study can provide the reference of theory and experiment for detecting other volatile organic compound gases.