Externality refers to the fact that when a certain production or consumption behavior brings additional costs or benefits to others, the person who exerts the effect does not pay a price or accept a reward for it. The externality of ecological products refers to the fact that those who demand ecological products or enjoy the ecosystem do not pay or do not fully pay the relevant fees, resulting in free or low price enjoyment or damage to the ecosystem. The externality is one of the important reasons for the insufficient supply of ecological products, and the realization of ecological product value is an important mechanism to solve the environmental externalities and safeguarding the functionality and integrity of ecosystems. Drawing upon public goods theory and externality theory, this study clarifies that ecological products possess characteristics such as complex value, public attributes, and uneven transaction externalities. Employing comparative analysis and deductive methods, the research explores the externalities and mechanisms of value realization of ecological products under different policy instruments, establishing a theoretical framework for internalizing the external benefits of ecological products. The findings indicate that: (1) Through the analysis from theory to practice, from vertical time evolution to horizontal path pattern, it is shown that the realization of ecological product value and the internalization of external benefits are highly coupled in terms of theoretical foundations, developmental processes, practical pathways, and implementation models; (2) Internalizing the external benefits of ecological products relies on the carrying capacity of supply and demand, constructing mechanisms from the perspectives of natural ecosystems and socio-economic systems, such as resource base-property relations-resource attributes at the natural level and developmental environment-participating entities-developmental patterns at the societal level, in order to achieve the dual goals of sustained expansion of external benefits of ecological protection and efficient promotion of internalization of production costs; (3) A theoretical framework for internalizing external benefits of the ecological products is established from three dimensions: ecological, social, and spatial, encompassing resource attributes-social factors-supply-demand space in a "4+3+3" structure. This framework includes resource attributes: improving the value realization path of various ecological products; social factors: integrating institutional environment, participating entities, and implementation models; supply and demand space: protecting and repairing supply space, regulating demand space, promoting supply-demand balance, and strengthening regional cooperation. This study elucidates the mechanisms of internalizing externalities of ecological products and provides theoretical insights for the precise and efficient realization of ecological product value through the constructed framework of internalizing external benefits.