Abstract: Against the backdrop of escalating global climate change and worsening water environmental pollution, advancing the synergistic reduction of pollution and carbon emissions in the watershed-coastal water environment has emerged as a critical research frontier in the field of ecological and environmental management. The present study summarized the migration and transformation processes of key biogenic elements such as carbon, nitrogen, and phosphorus, the carbon cycle, the synergistic relationship between pollution reduction and carbon mitigation, the technological system and governance policies for synergistic pollution and carbon reduction in the in the watershed‑coastal water environment systematically. Additionally, the challenges and deficiencies faced in the synergistic reduction of pollution and carbon emissions in the watershed‑coastal water environment were also addressed. Based on this, it is proposed to take the land-sea coordination concept as the core, construct a full-chain prediction model for pollutant migration and carbon cycles covering “watershed–estuary–offshore waters”, and establish a multi-index evaluation system for the synergy of pollution reduction and carbon mitigation. It is essential to enhance the capabilities of whole-process monitoring and numerical simulation for pollutant transport and carbon cycling, improve the integrated technical system and incentive mechanisms for land-sea holistic governance, and refine the carbon emission accounting and ecological compensation mechanisms for watershed-coastal systems. Furthermore, the coordinated implementation of pollutant discharge rights trading and carbon emission rights trading systems should be deepened, so as to form a closed-loop framework for synergistic pollution and carbon reduction in watershed-coastal water environments with technological innovation as the core and policy mechanisms as the guarantee. Through integrated land-sea governance, coordinated source-sink regulation, and the integration of technologies and policies, the synergistic benefits of pollution control and carbon abatement in watershed-coastal zones can be continuously improved, providing solid technical support for achieving the national carbon peaking and carbon neutrality goals across water environment.