Dong was granted a work permit in December, and his new contract will keep him with the Premiership leaders until 2010.
Manchester United signed Dong from Dalien Shide in January 2004 for £3.5m.
Manchester United manager Sir Alex Ferguson told the club’s website: “We’re all excited he has eventually arrived and can start playing.”
He added: “He sacrificed two-and-a-half years at Antwerp, which showed great patience and determination.
“He’s quick, athletic and he can only improve by training with the first team squad here.”
