The cargo was delivered on board the 266,000 cubic metres capacity Q-Max LNG carrier, the "Zarga", CNOOC said.
Mechanical completion of the first phase of the Ningbo LNG terminal, located just south of Shanghai, was achieved after almost two-and-a-half years of work at a cost of more than $1 billion.
The terminal facilities currently comprise one jetty to receive the largest carriers and three 160,000 cubic metres capacity storage tanks.
The Ningbo terminal's second phase is scheduled for completion in 2015 and will double the annual receiving capacity to 6 million tonnes of LNG per annum.
The first LNG cargo is being used for the terminal's cool-down and a second cargo is also scheduled for October, CNOOC said.
CNOOC will now be the operator of four LNG import terminals, adding to its facilities Fujian, Guangdong and Shanghai.
The other two terminals in China, at Dalian and Rudong, are operated by PetroChina and local partners.
China's LNG imports are forecast to be around 15 million tonnes this year, and gradually rising year-on-year to 40 million tonnes by 2020.