The ship on the sea has the phenomenon of swing under the combined action of sea waves, wind and its stability system in the case of synthetic aperture radar (SAR) imaging, which makes it difficult to focus. In order to correct the twodimensional (2-D) spatial variance and accomplish the imaging of swing ship, this paper proposes a new imaging algorithm based on spatial variant phase gradient autofocus (SV-PGA). Firstly, the entropy difference is used to determine the specific position of the ship. Then the ship image is extracted and segmented by a variable-size segmentation strategy. PGA is used to focus each sub image, and a well-focused ship image is obtained. The results of simulation experiments and real data show that the algorithm has good focusing performance.