A Secret Service affidavit filed in Miami federal court identifies the man as 20-year-old Joaquin Amador Serrapio Jr.
The affidavit says Serrapio posted the threatening comments under the Facebook name "Jay Valor" during Obama's visit last week to the University of Miami. One of the comments says "Jay Valor" would put a bullet through the president's head and everyone should watch on YouTube.
There's no indication Serrapio took any steps to carry out the threat.
Serrapio was free Tuesday on $70,000 bail with an arraignment scheduled in March. His court-appointed attorney declined comment.