China has opened the world's longest cross-sea bridge.

The Jiaozhou Bay bridge is 42 kilometres long and links China's eastern port city of Qingdao to an offshore island, Huangdao.

State-run CCTV says the 35-metre-wide bridge is the longest of its kind and cost about $1.5 billion Cdn.

CCTV says the bridge passed construction appraisals on Monday and the bridge and an undersea tunnel opened to traffic on Thursday.

It has taken four years to build the bridge, which is supported by more than 5,000 pillars.

According to the Guinness World Records book, the previous record-holder for a bridge over water is the Lake Pontchartrain Causeway in Louisiana. The Chinese bridge is more than four kilometres longer.