Zhang Xinyan, 35, had drunk four draught beers before deciding to enter the Beijing Zoo pen belonging to six-year-old male panda Gu Gu.
The startled Gu Gu bit both legs of his intruder, who responded by biting "the panda on its back", Mr Zhang was quoted by state media as saying.
Mr Zhang said he had not realised pandas could be violent.
He told the Beijing Morning Post that he had come to the Chinese capital "only to see the pandas".
"The seven-hour train ride was exhausting, and I drank bottles of beer when I arrived then had a nap," he added.
While bleeding half to death in a hospital bed, Mr. Zhang reported the real tragedy of the day had been that his bite was not forceful enough to penetrate his hairy-backed opponent.
Mr. Zhang was quoted as saying, "No one ever said they would bite people. I just wanted to touch it." Good thing he was only four sheets to the wind -- and he wasn't there to see the rhinos.
— Red, I've Bitten a Man for Less, Panda Light Reading