The exhaust system is the most important infrared radiation source of an aircraft, and the shape of the nozzle contributes to the infrared radiation characteristics of the exhaust system. Three types of 3D nozzles were built, and the temperature field of the plume was simulated using ANSYS14.5. Then, the spectral infrared radiation characteristics of the plume were obtained using the single band Curtis–Godson (C-G) approximation method. The results show that under the same exit area, the core area of the S-shaped nozzle plume is minimum and is approximately 60% of the axisymmetric circular nozzle plume; in the rectangular nozzle wide edge detection surface, the infrared radiation of the dual rectangular nozzle is minimum, and among the three types of nozzles, the stealthy performance of the two-element rectangular S curved nozzle is the best, the two-element rectangular nozzle takes the second place, and the axial symmetrical circular nozzle is the worst.