Marine ecological resources are the foundation of social and economic development. A nation′s marine economic development mainly depends on the quantity and quality of marine ecological resources it possesses. Marine ecological resources, as the important input to marine industry, can be viewed as “capital”. According to the World Bank′s definition, capital consists of natural capital, man-made capital, human capital and social capital. Marine ecological resources are the important component of natural capital. Valuation and capitalized management of marine ecological resources are very important for human′s sustainable development. This article proposed the concept of marine ecological capital based on the theories of both natural capital and ecosystem services. At the same time the authors consider the definitions of “natural capital” and “ecological assets” defined by national and international scholars and also the special characteristics of marine ecological resources. Marine ecological capital was defined as marine ecological resources which have direct or indirect contributions to humans′ social and economic production and provide benefits for humans. The value of marine ecological capital is defined as the monetized benefits for humans from marine ecological capital, including marine ecological resource stock value and marine ecosystem service value. Marine ecological resources consist of marine living organisms and their habitats (i.e. seawater, surface seabed), as well as the marine ecosystem and they act as a whole. Marine ecological capital has the general attributes of capital as well as its own attributes. General attributes include the overall and long-term profitability, the nature of production input and scarcity. Marine ecological capital′s attributes include threshold, holistic nature, mutual promotion and restraint, spatial-temporal complexity, mobility, across-region transfer, incomplete ownership, public goods and externality. The marine ecological capital concept is different from marine ecosystem services, marine ecological assets, marine natural capital, and marine resources. Marine ecological capital is the stock form of marine ecological resources. Two groups of marine ecological resources, including marine living organisms and habitat, compose the entirety of a marine ecosystem. The product flow and service flow provided by marine ecological resources, known as marine ecosystem services, are flow forms. The benefits of marine ecological capital are mainly realized through the way that marine ecosystem provides services for human. Therefore, the value of marine ecological capital consists of its stock value and marine ecosystem service value. However marine ecosystem services, as a revenue flow generated by the marine ecological capital, are different in content and form from marine ecological capital. Marine ecological capital and marine ecological assets is a pair of terminology easily confused and often misused. They both mean marine ecological resources stock forms that can product benefits. Capital is an economics term whose key attributes are the natures of profitability and production input. Asset is accounting terminology, whose basic attributes are the nature of profitability and the property right. Asset emphasizes on the property right rather than nature of input for production. However the term capital emphasizes on the nature of input for production rather than the property right. Marine natural capital refers to marine natural resources which generate benefits for humans, including marine living organisms, seawater, seabed, marine minerals, ocean energy, and the entire marine system which they integrate into. These natural resources are linked as an entirety together through long-term, global-scale seawater cycle, biogeochemical cycle, geological process and atmospheric circulation. However marine ecological capital refers to marine ecological resources which generate benefits for humans, including marine living organisms and their habitats and the entire marine ecosystem. These ecological resources are linked together by short-term, local-scale biogeochemical processes and ecological processes. Marine ecological capital is an important part of marine natural capital. Marine ecological capital and marine resources are two obviously different concepts. The former includes marine living organisms and their habitat and the entire ecosystem they compose. The latter includes marine living organisms, seawater, minerals, ocean energy, ocean space and marine tourism resources, without focus on the biological coupling relations around marine organisms, sea water and surface seabed.