This paper explains CO2 fixing mechanisms in coral reefs and technologies to construct coral reef eco-factories. A coral reef fists CO2 through two routes of photosynthesis and calcification, with both processes proceeding conjugately. Calcification is driven by the photosynthesis that proceeds at a rate more than ten times faster than the calcification. The Geological Survey of Japan is working on elucidating CO2 fixing mechanisms in coral reefs and studying coral reef eco-factory structuring technologies to utilize the capability of the mechanisms at a possible maximum extent. This study is directed to optimizing site conditions for coral reefs, optimal arrangements and environmental conditions for clusters, and production process determining factors. The structuring technologies may include controlling water temperatures, water flows, nutritious salts, and suspended substances that match optimal CO2 fixing conditions in coral reefs; seeding technologies for coral reef organisms; aquaculture techniques utilizing fixed CO2; combination with cultivating techniques; and combination with new energy technologies including sea water temperature difference power generation to control water flows and maintain facilities. 4 refs., 5 figs.