Abstract: Since the hardware-in-the-loop (HWIL) simulation systems are designed only for one seeker to one simulator, a five-axis turntable simulation scheme with a zoom projection optical system is proposed. The HWIL simulation systems can be applied to the seekers which have different optical parameters, so it is more cost effective. The characteristics of the zoom projection optical lenses in HWIL simulation system are outlined. The infrared zoom system whose diffraction is limited in the wavelength range of 8m～12m is designed. The zoom ratio of the system is 3.0, and the diameter of spot dispersion is less than 50m.