Sea-land coordination is an integrated task for optimizing the distribution of industries, space, people, resources, environment and other elements of the two major subsystems of sea and land. It is of great significance to ensure the efficient and coordinated development of coastal areas. With the emergence of the regional network development model emerged, a new round of territorial spatial planning has been gradually implemented. On the one hand, sea-land coordination has been given new connotations. On the other hand, sea-land coordination is facing new problems and challenges. There is an urgent need for an optimized path of territorial spatial planning in China's coastal areas under the "space of flows" paradigm. The paper combs the practice process and the evolution of related policies of sea-land coordination in coastal areas at home and abroad. And on this basis, the paper clarifies the conceptual connotation of sea-land coordination under the background of the new round of territorial spatial planning. Aiming to tackle the key challenges, the paper proposes a practical path to optimize the sea-land coordination. The study concludes that: (1) China's coastal areas have experienced a sea-land coordination practice and policy evolution path from "point" to "point-line" to "point-line-surface". Under the background of the new round of territorial spatial planning, the connotation of sea-land coordination is a "space of flows" strategic thinking that develops and protects all elements of the whole territory. Through unified planning of resource element allocation, industrial linkage, habitat co-governance, spatial interconnection and institutional inter-embedding of the two major marine and land systems, the coordinated and efficient development of coastal areas will be promoted, and the quality of production, life and ecological space will be improved. (2) As an important part of territorial spatial planning in coastal areas, sea-land coordination mainly faces four key challenges in practice: unclear sea-land spatial boundaries, uncoordinated sea-land economic systems, ununified sea-land resource development and habitat protection, and unbalanced sea-land spatial planning systems. Compatibility, at the same time, these are also the main cruxes of the disorderly development of space in coastal areas. (3) Practical path for sea-land coordination: clarify the boundary and target positioning of the overall plan; divide the functional space and optimize the spatial layout of the coast; build a systematic ecological protection system to improve the coastal ecological environment; coordinate the allocation of multiple elements to promote the coordinated economic development of coastal areas; improve planning system to ensure integrated management of land and sea. What needs to be pointed out is that any space-related mechanism and policy has scales. Undoubtedly, as a marine and land space development and protection strategy, sea-land coordination must have a scale. Sea-land coordination of different spatial scales has different strategic priorities and planning goals. Therefore, the scale conversion thinking should be strengthened when we formulate sea-land coordination policies. Finally, it is expected that the results can provide a reference for the coordinated development of sea and land in coastal areas of China.

With the deepening of the structural reform of ecological civilization system, the control on the use of territorial space has been widely recognized as a solution to overcome the constraints of resource and environmental factors. Territorial spatial planning and use control features strong correlation, integrity and being carried out in stages, in terms of their content composition, function and implementation process, which makes the formulation of territorial spatial planning an important part in the implementation of use control. Currently, the research on marine spatial planning under the background of territorial spatial planning generally focuses on the integration of the concept and form of land and sea planning, but inadequate consideration of the particularity, complexity and independence of the sea has led to the deficiency of policy basis and technical guidance for the formulation of the sea-related planning in coastal areas. Therefore, it is of practical necessity and urgency to strengthen the study of marine spatial use control under the planning perspective. Through concept comparison and connotation extension analysis of use control, the core content of territorial spatial use control, namely zoning and control rules, is clarified and elaborated: (1) In terms of zoning, a three-level marine spatial zoning system is proposed, considering the compatibility of marine spatial functions/uses, sea-use diversities, the large-scale nature of development and utilization, and the negative regional externalities, etc. Based on the understanding of the purpose and the mechanism of territorial spatial zoning, it is believed that we should established a marine spatial zoning system on the basis of scientific understanding of the objective attributes and evolutionary laws of the ocean, and then put forward the technical logic of three-level marine spatial zoning based on "double evaluation". (2) In terms of control rules, firstly, coordination of the relationship between development and protection is identified as the current core mission of marine spatial use control, and then four basic questions faced are raised, namely, "how to protect", "how to use", "how to use in protection" and "how to protect in use". "Double evaluation" has the characteristics of constraining and developmental coupling in value orientation, which coincidently conforms to the 2-dimensional nature of marine development and protection. Therefore, we create a two-dimensional coordinate system, taking the importance of ecological protection as the vertical axis and the development and utilization demand as the horizontal axis, as a tool to elaborate on the policy and content orientation of the use control in different marine function/use areas. The above research is expected to support the deepening of the theory and technical methods of marine spatial planning and use control.