The man in his 20s fell to the ground following a planned explosion while performing an aerial stunt on set at Leavesden Studios north of London, during filming of the last Potter film, Harry Potter and the Deathly Hallows.
"The guy was rigged up to a harness for the scene and was flying through the air. It is thought he may have been caught by the explosion and hit the ground very hard," a source said.
"Everyone is just hoping he makes a good recovery."
A spokesman for Leavesden Studios confirmed a member of the Harry Potter production team was injured.
"We are awaiting further news. Out of respect for the family we are unable to comment further," he told the Daily Mail.
A Warner Bros spokesman told the BBC the man had been taken to hospital.
The Harry Potter series of books by J.K. Rowling have sold over 400 million copies, been translated into 67 languages, and spawned a successful series of films and a theme park.