The cargo, which was sold by the National Iranian Oil Co (NIOC) to Trafigura, was loaded in late June, Reuters reported Monday.
The Olympic Target, carrying Iranian crude, is expected to arrive in eastern Shandong later this week.
Trafigura, the world's second-biggest independent oil trader, declined to comment on this, while NIOC could not be immediately reached for comment.
But sources said the sale was agreed on condition Trafigura would market the crude to Chinese teapots, which are outside NIOC's usual Chinese clients.
Early in July, Mohsen Qamsari, the director for international affairs of NIOC, said Iran had sold 2 million barrels of crude to Poland.
On June 27, the Atlantas Very Large Crude Carrier (VLCC), destined for Gdansk, left Iran's Kharg Island laden with 2 million barrels of crude.
The cargo was the first Iranian crude sold into this part of the Baltic Sea market following the removal of anti-Tehran sanctions.
The sanctions were lifted after Tehran and the Group 5+1 (Russia, China, the US, Britain, France and Germany) on July 14, 2015 reached an agreement on Iran’s peaceful nuclear program and started implementing it on January 16.