The IR simulation technology of irregular objects, such as smoke, dust, cloud, flame and so on, is one of the key technologies and difficulties of real-time IR image generation. Take the IR simulation of smoke for example, first, the shape of the smoke was modeled based on the Navier-Stokes equation, the method of initialization and boundary processing was also provided. Then, the infrared model of the smoke which take into account the smoke′s own radiation and the sun′s radiation was built based on the gray body radiation model and the light projection algorithm. Last, the smoke IR simulation based on the physical model was implemented using the CUDA parallel computing tool, and the IR smoke was successfully embedded into the IR scene based on Vega, also, the effects of the IR smoke based on the physical model and the Vega particle system were contrasted. The results indicate that the smoke IR simulation based on the physical model can meet the requirements of real-time, and has the advantages of strong sense of reality and good controllability.