The terahertz band is the natural extending of the microwave from millimeter wave to the high band, more and more attention is attracted to the development of the terahertz radar, even more important is that there many special physical properties present at the terahertz band, the revolutionary breakthrough at the imaging resolution and imaging frame is expected at the Terahertz SAR. There are many differences between the terahertz SAR and the traditional microwave SAR, the most crucial difference is the treatment of the motion compensation. Although the motion compensation the key technology of SAR at any wave band, the motion compensation of the terahertz SAR becomes so critical, because of the wavelength of the terahertz wave is so short, the high frequency vibration of the radar platform should be treated carefully. The idea of how to treat the ordinary motion error is introduced at first, the impact of different type of motion error to the terahertz SAR is analyzed next, final comes the analysis of the impact of high frequency vibration to the terahertz SAR, a solution is proposed.