Dong leaves Man Utd by mutual consent
The 23-year-old was the first Chinese player to join United when he left hometown club Dalian Shide in January 2004.
The Chinese international spent two years on loan at United's Belgian feeder club Royal Antwerp until he was eligible to play in England.
"Dong Fangzhuo's United contract has been cancelled by mutual consent," United said on the official club website.
The player struggled with injuries during his time at United.