How can countries identify comparable competitors and find like-minded partners in the international trade market of blue products to achieve better blue economic growth? This paper maps the "Blue Country Space" (BCS) based on the differences in the export capacity of blue products possessed by countries and decomposes it through the hierarchical structure analysis of complex network, dividing countries into different hierarchies. The results demonstrate that countries with leading positions in the international trade market of blue products are at higher hierarchies in BCS, as evidenced by their diversification and comprehensiveness of blue products of different complexity. The paper therefore argues that better blue economic growth also implies a cascade leap in BCS. Countries should not voluntarily give up their original low-complexity blue products to achieve better development. They can also establish long-term trade partnerships through regional cooperation to enter higher hierarchies together with members in the same hierarchy. Different hierarchies reflect the differences in blue product portfolios of different complexity. Countries in the same hierarchy become the most direct competitors due to they have similar blue product export capabilities. While the competition between countries in adjacent hierarchies is relatively weak. There is no obvious competition between non-adjacent hierarchies, which tend to be more trade complementary. These findings suggest that the BCS can be used as a useful additional policy analysis tool. Each economy can use this tool to analyze differences with comparative foreign competitors. Learning from the experience of higher-hierarchy countries in managing ocean and coast industries, leading to reflections on the development of its own blue industrial structure, and contributing to the formulation of blue industrial policies by policymakers.