It′s significant to research the infrared radiation model and simulate infrared image of unmanned aerial vehicle(UAV). The interpolation calculation of skin temperature was realized, based on the database of steady-state temperature distribution of the UAV which was calculated in use of CFD. Due to the new method of grid number projection, the orthogonal projection of depth buffer was improved and a two-dimensional projection algorithm for infrared image was implemented. The IR model of UAV was finally built to calculate spectral and band of infrared image, in which atmospheric transmission and detector response were both considered. The UAV infrared characteristics of the whole trajectory and calculation speed of this model were analyzed. The simulation value was compared with the measured flight experiment data, the results show that the relative error is less than 20% and can be used for experiment test and analysis.