With the increasing permeability of micro-grids, power quality problems become more and more serious in a distribution network. The Unified Power Quality Conditioner (UPQC), as an integrated power quality control device, has been widely considered and has become one of the research hotspots of power quality enhancement. This paper mainly summarizes and analyzes the topology, detection methods and control strategies of the UPQC. The research and development of the UPQC at home and abroad is illustrated, and the trend of its technology development is forecasted. This may be of significance for follow-up research. With continuous research progress, the UPQC will have better ability to improve the power quality of distribution system in micro-grids. This work is supported by National Natural Science Foundation of China (No. 51477070).