A new method to simulate and test the closed-loop performance of an IR imaging seeker by using digital image injection was proposed. The detector of IR imaging seeker was replaced by image emulation and injection devices in the simulation condition, so the performance of tracking servo loop was likely to be different from that under the actual condition. To allow the results of the digital image injection to be close the simulation experiment, an evaluation index system and an evaluation method for the consistency capability of the tracking servo loop under the simulation test and an actual condition were established to improving the precision and reliability of simulation test result. Then, the accurate tracking servo system model of an actual IR imaging seeker was setup, and a hardware-in-the-loop simulation test system of digital image injection system was established. The experiments was performed on a seeker platform and the capability limits of the hardware-in-the-loop simulation test of digital image injection system was found by adopting the simulation and modeling combined with the experimental test method. The result shows that the tracking performance of the seeker can be held in consistency under the above two conditions when the maximum random maladjustment angle error is 0.18°, the maladjustment angle delay and the maximum angle velocity of the target are smaller than 73 ms and 1(°)/Hz, respectively. These results provide a foundation for forming the capability of the digital image injection simulation test for infrared imaging guidance weapons.