The invention provides a space target ISAR range alignment method based on range migration trajectory. An equation set is established by extracting range migration trajectory edge information and combining a target equivalent motion model; and according to the global entropy minimization criterion, an equivalent rotation center is estimated, and range offset amount of a target is obtained, thereby realizing space target echo range alignment. The method has higher accuracy, does not introduce distance bias errors and high-frequency phase errors in the range alignment process, and provides favorable conditions for the application of a follow-up large-rotation angle high-resolution imaging method.