In order to meet the needs of high-precision simulation images in the development process of infrared imaging detection system, the infrared physical imaging radiation transmission model for aircraft was established, and the ray tracing method was used to realize the simulation calculation of radiance image. Aiming at the difference between the reflection characteristics of the aircraft skin and the distribution characteristics of the radiation source, an optimization method for skin radiance calculation using direct lighting multi-importance sampling was proposed. Aiming at the characteristics of strong emission ability and weak extinction ability of aircraft exhaust plume, an optimization method for exhaust plume radiance calculation using combining integration was proposed. The correctness and effectiveness of the physical imaging model and calculation optimization method were verified through simulation experiments. The relative error of the skin radiation calculation is better than 0.05%, and the relative error of the tail flame radiation calculation is better than 0.1%. Compared with the traditional ray tracing method, the calculation optimization method has a faster convergence speed and stronger adaptability. Infrared imaging simulation and radiation characteristics analysis of stealth aircraft were carried out. The simulation results show that infrared stealth technology can reduce the radiation intensity in the mid-waveband and long-waveband, and increase the reflected radiation intensity in the short-waveband.