Building a Sea-power is not only beneficial to the security and development of the sea-related countries, but also the key to safeguard and expand overseas interests, and it is supposed to be an effective way to shape a global power. In view of this, this paper attempts to combine the overall trends and the periodical changes in the marine era, comprehensively consider the universality and particularity of the Sea-power strategy, and build a feasible theoretical framework for the Sea-power strategy. Therefore, it will take the interaction of the marine needs and capabilities as core hypothesis, take the objective environment (historical trend, geo-structure and order process) and subjective positioning as intervening factors, and take the strategic goals and strategic measures as intervention variables. With that, the paper aims to explain the following conclusion with deductive reasoning: (1) The Sea-power strategy can not only promote the process that builds a stronger sea-related country, but also achieve the result that the sea-related country becomes stronger. (2) The fact that the sea-related countries fail to build itself into a Sea-power is due to the negative interventions of objective environment and subjective positioning, which makes the interaction between marine needs and capabilities does not match in a positive way. (3) Strategy is the best key to the relationship between the sea-related countries and the Sea-power, but its utility is limited.