Abstract: "Land and sea coordination" holds vital significance to realizing the national strategy of "developing national strength via marine development" and ecological civilization construction. In the process of recognizing this terminology from a policy term to a legal term, more and more legislations have reflected this terminology as a legal concept and principle. But to achieve its transformation from a policy term to a legal term in the real sense relies on the clarification of its legal intention. Combining general semantic definitions and existing norms, "land and sea coordination" means that the government should coordinate the action deployment and interests between the land and marine economic and social development and the eco-environmental protection in accordance with the requirement of overall planning and comprehensive coordination. In essence, "land and sea coordination" aims at providing the guiding principle and normative restriction for the government's coordination of the land and sea resource development and utilization with the eco-environmental protection. To realize the theory and principle of "land and sea coordination" calls for the reflection of this requirement in legal norms at different levels, clarification of the legal system to support its objectives, and response of the legal assessment system to the requirement of "land and sea coordination".