Abstract: The ambiguity-to-signal ratio (ASR) is an important performance requirement for spaceborne synthetic aperture radar (SAR) system. A novel ambiguity echo simulation method for spaceborne SAR was proposed to analysis the impact of the ambiguity on SAR image quality quantitatively. A novel spaceborne SAR ambiguity echo model was utilized in the method. The SAR echo from both the observation zone and the ambiguity zone can be generated with this method. The SAR image with ambiguity characteristic can be acquired by applying imaging processing to the echo data. The method is an effective tool for studying the relationship between the ASR and image quality. It can reflect the geometric character of the target in the ambiguity zone, which provides reference for SAR image interpreting. The computer simulation validates the proposed method.