Due to great advantages in anti-stealth and wide bandwidth, the Terahertz Inverse synthetic aperture radar (THz-ISAR) imaging technique has attracted much attention in recent years. However, high resolution will intensify the dispersion effect especially for high-speed moving targets. This paper presents a new method of high speed motion compensation for THz-ISAR imaging. The proposed entropy-based method is capable of auto focusing the image in several iterations, which avoids using the time-frequency distribution. Its superiority is compared in simulation experiments.