Mega-Delta Programme, endorced as part of the UN Decade of Ocean Science for Sustainable Development, has the overall objective to support sustainable development in delta regions. Integrated framework of observations and numerical modelling system, supported with the newest technology of big data management and artificial intelligence for data analysis, is becoming the right way to guarantee the success of the Mega-Delta Programme. Therefore, as the leading institute of Mega-Delta Programme, the State Key Laboratory of Estuarine and Coastal Research in East China Normal University decided to promote the development of the Digital Twin of Estuarine and Coastal System, in order to better serve the scientific research, engineering applications and emergency management on the mega deltas over the whole world. The first step is to develop the digital twin system of Yangtze River Estuary, based on the solid foundation of observations and multi-disciplinary modelling systems. So far, the development of digital twin system of Yangtze River Estuary confronted great challenges ranging from the understanding of conceptual models, integrating core technologies and creating application scenarios. This event is the first symposium on digital twin of estuarine and coastal system, and the aim is to enhance the understanding and exchange ideas of the digital twin of estuarine and coastal system. This symposium has received the special invitation from the digital twin of the ocean program which is endorced as part of the UN ocean decade. Currently it is listed as one of virtual satellite events in the international digital twin of the ocean summit.