The nonuniformity of an infrared scene simulator based on a digital micro-mirror device(DMD) is one of the major factors affecting its performance, and it must be corrected to satisfy the application requirements of the simulation testing of infrared imaging equipment in complex environments. The nonuniformity correction flow of an infrared scene simulator based on a DMD was investigated in detail. A method for measuring the nonuniformity of a variable scale sparse grid was used to fit the test conditions better. Offline data processing based on linearization and segmentation correction was introduced, and real-time nonuniformity correction based on online table lookup was adopted. The simulation shows that the nonuniformity can be reduced to approximately 0.5% by the variable scale sparse grid measurement and real-time nonuniformity correction. The infrared scene quality of the infrared scene simulator based on a DMD improved significantly.