Abstract: Flexible distribution networks are promising solutions to improve the operation performance by coordinating the diverse resources of distributed generators and loads. Soft open point（SOP） is considered as the essential equipment for realizing flexible distribution networks. In recent years, researches on the SOP operation control have been widely conducted and achieved abundant progress. This paper starts from the development trend of flexibility of the distribution network. The technical forms and application forms of SOP and its derived flexible interconnection concepts in multiple scenarios are reviewed and sorted out. On this basis, the key technical issues on SOP integration in flexible distribution networks for operation optimization, self-healing control,and configuration planning are explained, followed by a summarization of the current works.The development trend of SOP in the future is prospected, which provides ideas for the further expansion and deepening of the research and application of SOP technologies.