The analysis of radar targets in micro-motions is an emerging technical hotspot in the field of radar target acquisition and identification, and much progress has been made during this decade. Some scientific issues related to micro-motion analysis are discussed in this paper, such as the modulation in radar returns induced by micro-motions, the extraction of micro-motion features, the radar imaging for targets in micro-motions, and the radar waveform designing oriented to micro-motion features. Some of the research achievements have already applied in the fields of aerial and spatial target acquisition and identification.