In order to reduce the false alarm probability of low earth orbit missile early warning satellite, on the basis of analyzing the infrared radiation characteristics of the active section of ballistic missile, infrared imaging characteristics of missile active section were described through the establishment of the geometric feature model and infrared feature model of tail flame. By using the model, the infrared radiation distribution of tail flame was calculated, and the simulation image of missile tail flame was constructed. Simulation images could accurately reflect the real situation of the infrared image of missile tail flame, and provided important references for effective identification missile and improving the accuracy of missile early warning.