In order to measure the concentration of alcohol gas in the drunk drivers’ breath more accurately and quantitatively, the bi-spectrum laser remote sensing detection method was used to detect the concentration of alcohol gas and water vapor at the same time, and the dilution coefficient of the alcohol gas in the vehicle was simultaneously obtained. The inversion algorithm of alcohol concentration and water vapor concentration was carried out. The dilution coefficient was calculated theoretically and the absorption spectrum was verified by experiments. The spectrum absorption characteristics of alcohol gas and water vapor were obtained. The results show that, the laser wavelength are determined to be 1392nm and 1412nm. The method can eliminate moisture interference and obtain the dilution coefficient of alcohol gas, which can more accurately and quantitatively measure the concentration of alcohol in exhaled gas.