Shape and size estimation of space debris is an important issue of space debris observation. Generally speaking, space debris is prolate, and follows a simple roll rotation motion around the major axis. In virtue of its own shape and motion features, a two-dimensional radar imaging method of small space debris employing low resolution radar is proposed in this paper. The method recurs to time-frequency analysis technology to obtain the time-instantaneous Doppler distribution of all Scattering centers on the target, and then rearranges the distribution according to aspect angles to acquire target's cross range-aspect angle distribution, and finally reassigns respective points' power in the cross range-aspect angle distribution to gain target image. Furthermore, the paper analyzes the impact of reference center's uniform accelerated motion relative to radar on imaging, and presents corresponding solutions. Simulation results reveal the validity of the method, and target image has a resolution of approximate wave length.