Abstract: In order to popularize the application of supersonic swirling separator technology in the natural gas liquefaction field, theoretical and numerical study on the supersonic flow and liquefaction process of methane-ethane bi-component system within Laval nozzles were carried out. The effects of the inlet temperature, inlet pressure, back pressure and the components composition on the liquefaction process were analyzed by Fluent software, basing on the flow control equations. The results show that the critical liquefaction temperature and pressure of methane-ethane bi-component system will decrease with the appropriate decrease of inlet temperature or increase of inlet pressure, and the range of gas-liquid two-phase region or the liquid phase region will enlarge, which will promote the liquefaction process. The temperature of critical state of bi-component system is 330 K. Shockwaves will generate in nozzles when the back pressure is higher than 20%, resulting the abrupt temperature and pressure change in nozzles. As a result, the liquefaction environment will be destroyed. The pressure and temperature for liquefaction decrease with the increase of methane content of bi-component system, so the region range in which the natural gas will be liquefied will narrow which brings more difficulty to the appearance of liquefaction.