Gu Gu first made news in 2007 when he bit a drunken tourist who jumped into his pen and tried to hug him. The tourist retaliated by biting the panda in the back.
In October, Gu Gu viciously bit a teenager who climbed into his exercise area out of curiosity.
The Beijing News said the latest victim, Zhang Jiao of central Anhui province, suffered damage to major ligaments and is recovering from surgery.
The newspaper quoted tourists as saying Zhang appeared to first look around to see if pandas were nearby before jumping in to get his 5-year-old son's toy.
Pandas, a national symbol of China and often seen as being cute and cuddly, can be violent when provoked or startled. Zoo officials have considered unspecified measures to prevent further incidents.
Police were investigating, and it was not clear yet if Zhang would face criminal charges, Gong said.
