Synthetic aperture ladar (SAL), whose carrier is laser, makes use of synthetic aperture processing to improve the resolution of images. Vibration from the platform of SAL will affect on the imaging quality of SAL. The effects of line vibration on the imaging quality are analyzed. Firstly, instantaneous range of synthetic aperture ladar with vibration is unwraped and the effect of vibration is divided into two classes, the along-track and the cross-track one. After analysis, the effect of the along-track vibration can be ignored while the cross-track one cannot. And the vibration only affects the azimuth direction result in defocusing of the azimuth and the imaging quality. Finally, the simulations prove the validity of the analysis.