Abstract: Traditional 3-D laser imaging systems are based on real aperture imaging technology, whose resolution would decrease with range's increasing. An advantage of synthetic aperture imaging technology over real aperture imaging is that the resolution of the imaging system is constant with range's increasing. In this paper, a novel 3-D imaging system was given, which was based on synthetic aperture technology. According to the characteristic of the signal, a suitable data progressing method was proposed based on the flood-light transmitting mode and multi-beam receiving mode. Firstly, in the range dimension, the signal with large time bandwidth product was adopted to obtain high resolution with the help of dechirp technology. Secondly, in the along-track dimension high resolution was obtained by synthetic aperture technology, in which the phase error caused by long scan duration was taken into account and compensated. Thirdly, in the cross-track dimension traditional real aperture array imaging method was adopted. Finally, simulation was provided to demonstrate the effectiveness of the proposed system.