The film, whose title translates as "The City of Golden Armor," is set in the Tang Dynasty (618-907) and is based on the renowned Chinese modern playwright Cao Yu's classic drama "Thunderstorm."
Li, 17, a student of the Central Academy of Drama, joined the cast including Gong Li, Hong Kong heart-throb Chow Yun-fat, mainland actor Liu Ye and Taiwan pop singer Jay Chou, Xinhua was told by Zhang Weiping, the film's distributor on Thursday
He said her "personality shown in the screen test" answers for the decision made by Zhang Yimou and other related staff.
"She is our most satisfactory candidate in terms of both acting and age," he said, adding that she also has a good basic training of dance.
In her film debut, Li will play a girl aged from 15 to 17, the counterparts of Si Feng in the drama "Thunderstorm."
Zhang Yimou is adept in boosting new actresses in his films, so his selection of the new actress, dubbed "Mou (Yimou) Girl," often triggers hot topics of the public and media.