The 22-year-old was returning voluntarily when he fell from a London to Brussels service in Cheriton, Kent, at about 5.50pm on Monday.
British Transport Police (BTP) said the incident was being treated as "non-suspicious".
There were long delays to the Eurostar service as police launched an investigation. Paramedics declared the man dead at the scene. Read More
Passenger Richard Ashworth, MEP for South East England
It defies logic, how you get a door open on a train at high speed