To verify the capability of infrared guided missiles against infrared decoy at less cost, the ability of infrared hardware-in-the-loop simulation should be improved. The infrared hardware-in-the-loop simulation based on MOS resistor arrays is one of the most effective simulation methods in many means. Infrared decoy is simulated by using a MOS resistor array and an infrared decoy model. Particularly, an infrared decoy motion model is established. Then, the theoretical model of infrared decoy established after the correction of the trajectory of infrared decoy is measured in the fields. The result shows that the realistic simulation of infrared decoy trajectory is the key to the effective verification and improvement of the capability of infrared guided missiles against infrared decoy.