This study aims to address the remote measurement requirements for multiple alkane gas leaks in petrochemical plant areas, taking into account the effect of water vapor spectra on alkenes spectra as most of these petrochemical storage tanks are located at the sea side. To eliminate the influence of water vapor and carbon dioxide in the air, the absorption peak of propane at an infrared wavelength of 3364 nm is selected. By using an ICL laser, simultaneous measurement of both propane and n-butane gases in this band is achieved. Furthermore, an open light range method is proposed where a reflective film is placed at a distance of 100 meters and the returned light is gathered through a lens onto a detector, thus enabling remote telemetry analysis of alkane gases at a distance of 100 meters. This paper presents data on the absorption signals and harmonic signals of the two gases at 100 meters. Based on the analysis of harmonic signals and noise, the detection limit for the gas to be tested is calculated to be less than 100 ppm·m.