The agency also said that China will soon sign another agreement with Boeing for the purchase of 80 more 737 jets.
Xinhua quoted a source at China Aviation Supplies Import and Export Group Corp, which handles government aircraft purchases, as saying the first group of planes will be delivered to eight Chinese airlines between 2006 and 2008.
The news agency said the airlines are Air China, China Southern Airlines, China Eastern Airlines, Shanghai Airlines, Xiamen Airlines, Shandong Airlines, Hainan Airlines and Shenzhen Airlines.
The signing was part of a broader deal to supply a total of 150 737 aircraft.
Plans for the additional 80 planes have not been finalized but deliveries will be after 2008, Boeing's China spokesman, George Liu, said, according to Agence France-Presse.
There were no details on the engines to be used on the planes.
The signing of the deal came as US President George W Bush and Chinese President Hu Jintao held talks in Beijing on a number of issues, including China's huge trade surplus with the US.
Bush had signalled before his visit that trade would be high on his agenda, with one of his main concerns being the US trade deficit with China, which is expected to surpass USD200 billion this year.
The latest deal adds to an agreement in January in which Boeing sold 60 of its new generation 787 "Dreamliner" passenger jets to China for USD7.2 billion.
It is a further boost for Boeing in its battle against European rival Airbus for market share in the world's fastest-growing major aviation market.
Boeing holds around 62% of China's aviation market. Airbus has a 28% share.
A senior Asian affairs aide on Bush's National Security Council, Mike Green, had said yesterday that the latest Boeing deal was imminent and that it showed US policy on trade with China was making progress.
"It's a very important thing and I think it's a testament to how our approach to China is yielding real results -- in this case, an order for 70 737 aircraft from Boeing," Green told reporters.