The issue of marine ecology is an institutional one. China \' s marine ecological protection system has gone through a process of development from scratch to existence and from less to more. However, there are still many problems to be solved, such as whether a variety of complex systems can form a joint force of gover-nance, and whether the rear system failures, deficiencies, and conflicts. Therefore, this paper reviews the evo-lution logic of China \' s marine ecological protection system, explores the complementary space of the existing system from the perspective of institutional complementarity, and analyzes the path of institutional reform of supplement, amendment, and coordination, to promote the effective transition of marine ecological protection system emphasizing quality over quantity. The evolution of China \' s marine ecological protection system can be divided into three stages: initial establishment, steady progression, and gradual transformation, showing a trend characterized by a changing governance mode from land-sea division to land-sea integration, a changing supervision mode from government only to multi-institution coordination, a changing safeguard mode from standard norms to the legal system. The internal motivation of promoting the evolution of the marine ecologi-cal protection system is the link age between the long-overdue institutional derived demand and supply, and between institutional cost constraints and institutional income drivers. Marine ecological protection is a com-plex and systematic project across regions and departments, and the link age between different ecological pro-tection systems is crucial. Based on the theory of institutional complementarity, this study finds that China \' s marine ecological protection system has great complementarity needs in three aspects:protection subject, pro-tection means, and protection process. Among them, the problem of a single unitary protection subject is mainly caused by the lack of system, the low efficiency of protection means is mainly affected by the lack of system adaptability, and the separation of protection process mainly reflects the contradiction of system incon-gruity and mismatch. Based on this, the supplement of China \' s marine ecological protection system should fo-cus on the government \' s responsibilities and the cultivation of multiple subjects. The revision of the system should focus on the further improvement of non-governmental mechanisms such as market incentives and in-formation disclosure. The coordination of the system should be based on the whole process from pre-regulation preparations to post-regulation review, in order to promote the effective connection and coopera-tion of policy tools.