The pipeline, which linked Turkmenistan with southern China, will boost supplies to the country's booming industrial zones in Shanghai, Guangzhou and Hong Kong.
The pipeline will have one trunk and eight branches. Three branches have been completed and the other five will be finished next year.
The pipeline starts in Huoerguosi on the China-Kazakhstan border, 670 km northwest of Urumqi, capital of Xinjiang Uygur Autonomous Region.
The annual natural gas transportation capacity of the pipeline is expected to be 30 billion cubic meters. It is designed to provide stable gas supply for at least 30 years.
Liao Yongyuan, deputy general manager of China National Petroleum Corporation (CNPC), said the project would optimise the country's energy consumption structure benefiting about 500 million people.
As of May 28 this year, the already finished lines had delivered 10 billion cubic meters of natural gas to about 18 provincial regions and about 100 million people, Liao said.
It is expected to help ease strained natural gas supply in the Pearl River Delta and the Yangtze River Delta.
And it is planned to be connected with natural gas lines already in use, resulting in a network totalling 40,000 km of gas pipelines, state-run Xinhua reported.
