Abstract: Focusing on the adaptability testing of IR seeker in complicated battlefield environment, a new closed-loop simulation test method of using digital image injection was proposed, the composing and principle of closed-loop simulation test system were analyzed. The detector of IR seeker was replaced by image simulation computer and injection device in the simulation condition, thus the performance of servo system was likely to differ from that under the actual conditions due to the image generation delay and miss distance error, which affected the precision and reliability of simulation test result. The influence of time delay and miss distance error on seeker's servo system by building servo system model was studied. The research result indicates that the influence of miss distance error on track precision is only 1.33%, the closed-loop simulation is feasible if time delay is less than 56.5 ms. The results of research provide theoretical support for actualizing closed-loop injection simulation test of IR imaging seeker.