<p>Through continuous practical exploration and optimization, the marine environmental governance system has become increasingly refined, embodying the concepts of stable structure, effective organization, and value-added efficiency. Marine environmental governance is gradually shifting toward collaborative governance, in which multiple stakeholders and complex interest relationships interact within governance actions. In response, this study employs a case study approach and in-depth interviews, drawing on collaborative governance theory and participation ladder theory, and integrates the practical experience of marine environmental governance in Qingdao City to construct a ‘structure–process’ analytical framework. The research finds that, based on the case of fishermen’s participation in green tide cleanup in Qingdao, their current involvement in marine environmental governance displays characteristics of institutionalization, digitalization, and organizational structuring. In practice, local governments mobilize societal participation through an administrative contracting system embedded in a bureaucratic hierarchy. Through empirical examination of structural and procedural dimensions, and by identifying pathways to strengthen multi-stakeholder participation, this study contributes to the formation of governance synergy, the enhancement of governance efficiency, and the advancement of a fully inclusive marine environmental governance system. It thus holds significant theoretical and practical implications for improving the effectiveness of marine environmental governance.</p>