The stratospheric airship has the potential as large observation area, long drift time, and better efficiency. It is expected in many different applications, such as reconnaissance and surveillance. The imaging difference between the stratospheric airship SAR (synthetic aperture radar) and the airplane SAR was compared. Aimed at the redundant pulse repetition frequency and the large-amplitude low-frequency trajectory deviation, an optimization scheme was proposed and verified by simulation. The simulation result shows that the proposed optimized motion compensation method can eliminate the influence of motion error for the stratospheric airship effectively.