A new laser ranging technology based on gas absorption spectroscopy is proposed.The frequencies of reference optical signals and measurement optical signals carrying gas absorption spectroscopy information are mixedand Fourier transform is used to extract optical path differenceso as to obtain the distance information.According to the deduced ranging principlesa ranging system based on laser methane remote sensor is designedand its ranging process is simulated and analyzed by Matlab software.The simulation results have verified the feasibility of the gas laser ranging technologywhich supplies a promising direction for developing gas laser radar.