May, 47, was helping pull fellow presenter Jeremy Clarkson's car out of a ditch when he fell and hit his head on a rock, The Sun reported.
The Daily Telegraph's motoring columnist was rushed to hospital where he was given a brain scan and put on a drip, the paper said.
May suffered severe concussion and was given stitches for a head wound, according to the report.
He was quoted as saying: "I stood in the line of where the tow rope went taut. I told the driver to move off and became part of a giant catapault.
May joked that the reason he was given a head scan was because "the Syrians were just excited to be able to use their new scanner".
He played down the ordeal, saying it was not comparable to his colleague Richard Hammond's accident in 2006.
Hammond was in a coma and nearly died after his dragster overturned at 300mph.
May's accident can be seen on Boxing Day on BBC Two when the three presenters recreate the 1,200-mile journey of the Three Wise Men.
