The IR imaging simulation of the warship in the background of sea and sky based on OSG is given in this paper.According to the theory of IR physics and heat transfer，the IR physical model of warship was built by angle factor method，and then the temperature field distribution and radiance field distribution of the ship surface were calculated.Refer to missile trajectory，the mathematical model of the distance between missile and target and the transmittance were obtained by the third order nonlinear exponential fitting algorithm.At last，real time rendering and the gradual change of ship surface grayscale in IR seeker view was done by the shader technology during the missile flies to the target.The simulation experiments show that the simulation effect is better.The change of ship surface grayscale is consistent with real situation when simulating terminal flying of the missile，and the result of simulation is credible.