Abstract: The margin effect of infrared heating array on the flux uniformity on spacecraft surface is discussed in this paper. By adding a margin heating array with a certain angle, the infrared heating array can be optimized and the flux uniformity on pacecraft surface can be improved. Three modes are calculated and analyzed based on the geometry models of Monte Carlo simulation with different angles, and a method is found to optimize the margin effect of infrared heating array, which would be useful for the design of infrared heating arrays in many ways.