Aiming at the characteristics of Medium Orbit Synthetic Aperture Radar (MEO SAR) that the radar trajectory is non-straight and ship targets are not cooperative, this paper proposed a high-resolution imaging algorithm for moving ship under MEO SAR system. Firstly, the characteristics of MEO SAR are analyzed. The accurate slant range model of MEO SAR is derived, and the echo phase error caused by moving ships is analyzed. Combined with range model and Doppler parameter estimation to estimate ship motion parameters and then modify the range model. According to the modified range model, the error caused by ship motion is compensated to perform imaging of moving ship. Finally, it is verified by experimental simulation that good imaging results can be obtained within the range of common ship targets at sea.