Abstract: The plume IR image simulation based on the particle system needed large computation and was difficult to be integrated with the IR calculation model. To solve the problem, firstly based on the chemical reaction formula, the gas fraction calculation model of the aero engine's plume was established, and the engineering plume flow field calculation method was improved. Then based on the figure envelope model, the simulation model of the plume IR image was established. And three relative problems were studied: how to establish the figure envelope, how to combine the figure envelope model with the flow field calculation model and gas IR lightness calculation model, and the relation between the figure envelope and plume IR image. Finally, the plume IR image was generated by numerical simulation. The results show that the plume IR image is defined by the high temperature gas of the core area;the plume IR image is unrelatable with the figure envelope when the envelope is enlarged to a certain extent;the plume IR image is generated more effective and accurate when the figure envelope is easy to be divided into meshes, is small but can reflect the plume radiation distribution characters.