The truck broke down as it reached the middle of the grade crossing and was stuck there for 15 minutes on Sunday evening, but there were no guards on duty to warn the train to slow down.
Members of the public tried to push the truck away from the track but to no avail.
The driver was unharmed, but the vehicle owner, Ngo Quy Suu, said: "It's completely damaged."
The crossing was opened by locals, who hire a guard to work there during the day.
Duong Van Dat, the guard, said his job was to drop the barrier when a train was about to arrive, but the accident happened at 6:30 p.m., after he finished work.
The locomotive was slightly damaged and the train was delayed by 20 minutes.
There are thousands of grade crossings across Vietnam, and most of them are opened illegally by local people, according to Vietnam Railways.