The flights came into effect yesterday (January 25th), with the two airlines jointly marketing services between Berlin and Beijing.
Hainan has been flying between the cities since September 2008, with Air Berlin having arranged connecting flights from a number of German cities - including Dusseldorf, Cologne and Munich - as well as Vienna and Zurich.
Commenting on the codeshare, an Air Berlin statement said: "The codeshare flights are sold on a reciprocal basis and operated under the relevant airline's own flight number.
"Customers benefit from a wider choice of flights and convenient connections."
Passengers who have signed up to the airlines' frequent flyer schemes have been able to use their air miles on both Air Berlin and Hainan Airlines' networks since November.
Air Berlin announced earlier this month that it had enjoyed a one percent increase in the number of passengers it carried in 2008 compared to 2007.