With the increasing production and use of natural gas, the supersonic nozzle has become focus of the impurity removal research. In this paper, the modified classical nucleation model is used as the condensation nucleation model, and the Gyarmathy growth model is selected as the droplet growth model. Based on the assumption of no phase slip and Eulerian two fluid model, the flow control equation of wet natural gas is established. By giving the selection criteria as a turbulence equation, the SRK real gas equation is used to carry out the corresponding numerical simulation. The required supersonic nozzle structure and grid number are designed and verified. On basis of the above, the variation of temperature, pressure, nucleation rate, humidity and nucleation rate with the distance X of the nozzle after the methane-carbon dioxide gas enters the nozzle is studied, and the effects of different temperature, pressure and gas component proportion on droplet number, humidity and nucleation rate are explored.