Tianjin Port and Tianjin Gas Group Co, a city gas distributor, will also invest in the floating storage and regasification unit (FSRU).
CNOOC, parent of Hong Kong-listed offshore oil producer CNOOC Ltd, did not specify the stake each company holds in the venture.
CNOOC said a planned a second phase for a traditional land-based LNG receiving terminal with an annual capacity of no less than 6 million tonnes was scheduled to be operational by about 2015.
China has been adding onshore receiving terminals along its east coast for imports of super-chilled natural gas shipped by tanker to meet surging domestic demand for the cleaner-burning fuel.
With growing competition among industry giants CNOOC, PetroChina Co Ltd and China Petroleum & Chemical Corp (Sinopec) and limited sites along the coast, companies have been turning to floating facilities.