Laser imaging system which can give anti-interference high-resolution three-dimensional image has been applied widely. For the sake of scan rate in imaging system, line scanner adopts sine scanning, at the same time isochronouse laser pulses output, and spatial light-spot distribution is not asymmetry. As a result, imaging geometry distortion occurs. In this paper, reason for geometry distortion is analyzed, and two amending algorithms are presented. It is satisfied that these algorithms are used in artificial image and lidar image. Comparison shows that the second algorithm fits further to image amending in lidar imaging system.