In order to study the condensation process of CH4-CO2 mixture gas in the supersonic nozzle, the physical and mathematical model of CH4-CO2 mixture of supersonic condensation process in the nozzle was given out based on the gas-liquid two-phase flow control equation, droplet nucleation, growth model and CO2 droplet surface tension, The effects of inlet pressure, inlet temperature and inlet CO2 fraction on the flow and condensation parameters were investigated. The results confirm the feasibility of using the supersonic separator for the removal of CO2 from natural gas. With the increase of the inlet pressure and the decrease of the inlet temperature, the condensation position moves forward, the maximum nucleation rate decreases and the liquid fraction of (CO2) increases. The increase of inlet CO2 fraction makes it easier to achieve spontaneous condensation but the liquefaction efficiency remains at 57%-58%. The liquefaction efficiency of CO2 in the supersonic nozzle can be improved by increasing the inlet pressure and decreasing the inlet temperature. (C) 2017 Elsevier B.V. All rights reserved.