The supersonic separator has proved to be an effective method to condense and separate CO₂ from natural gas, and the inlet temperature plays a vital role on condensation characteristics of CO₂ in the supersonic separator due to the instability temperature of wellhead natural gas. In this paper, the physical and mathematical models for the supersonic condensation process of CO₂ in the natural gas were established on the basis of CO₂ droplet surface tension, nucleation and growth model. The flow and condensation parameters were investigated under different temperature conditions. The results show that when the inlet gas pressure is 8.0 MPa, the inlet gas temperature is 280 K and the CO₂ content is 0.15, the condensation position is x=240.25 mm, the maximum nucleation rate is 1.14×10²¹ m^-3·s^-1, the maximum droplet radius is 2.146×10^-7 m, the maximum droplet number is 8.20×10¹⁴ kg^-1, and the maximum humidity is 0.0446. The decrease of inlet temperature makes the droplet reach a greater growth rate and a larger radius of droplet at nucleation. With the decrease of the inlet temperature, the condensation position moves forward, the maximum nucleation rate and the droplet number, the droplet radius and the humidity of CO₂ increase.