The EU-China Blue Carbon Horizon Programme is an international cooperative research initiative jointly supported by the Ministry of Science and Technology (MOST) of China and the Directorate-General for Environment (DG ENV) of the European Commission. The project is implemented independently yet in close collaboration between the Chinese and European sides. The Chinese component, titled "Carbon Sink Potential and Multi-functional Synergistic Enhancement Approaches for Coastal Blue Carbon Ecosystems" (abbreviated as BLUES-C), is funded under the National Key R&D Program of China's "Intergovernmental International Scientific and Technological Innovation Cooperation" key special project. Supported by the China-Europe Joint Flagship Initiative on Climate Change and Biodiversity, BLUES-C conducts joint scientific and technological research with the EU's C-BLUES project on carbon sink formation mechanisms, monitoring and assessment, and carbon trading related to blue carbon ecosystems. The Project is jointly undertaken by 18 European research institutions and 10 Chinese research institutions. Work Package 5—Blue Carbon Accounting Methodology, Trading System, and Integrated Management—is the management dedicated work package under BLUES-C. Its objectives are to develop a common greenhouse gas accounting methodology for typical coastal blue carbon ecosystems applicable in both China and the EU, promoting the inclusion of macroalgal beds into the national IPCC greenhouse gas inventory guidelines; develop blue carbon methodologies for China's CCER carbon market and establish a "Monitorable, Reportable, Verifiable (MRV)" blue carbon trading system mutually recognized by China and the EU; and propose an optimized paradigm for integrated blue carbon management in ecosystems, fostering regional industrial restructuring and sustainable community development. The project implementation period is four years (December 2023 to November 2027). The Chinese Research Academy of Environmental Sciences (CRAES) is the leading institution for Work Package 5, collaborating with Zhejiang University, Hainan University, and the First Institute of Oceanography of the Ministry of Natural Resources, among others, to jointly advance the tasks of this work package. Concurrently, Work Package 5 has established a joint working mechanism with European project teams, including the Norwegian Institute for Water Research (NIVA), the University of Malta, Bangor University (UK), and the Middle East Technical University (Türkiye), to conduct collaborative research on China-EU blue carbon management. By the end of 2025, Work Package 5 had drafted several technical standard proposals for blue carbon sink accounting and trading, co-authored one policy research report with the European partners, and published 4 SCI papers. The project's outcomes are expected to further promote the inclusion of blue carbon sink enhancement into the China-EU climate change policy framework and provide robust scientific and technological support for China's climate diplomacy negotiations.