Shaunia Hare was already dead when paramedics arrived at the home, said Lt Bobby Caruthers of the Sumter County Sheriff's Office.
He said Charles Jason Darnell, the snake's owner and the boyfriend of Shaunia's mother, discovered the snake missing from its aquarium and went to the girl's room, where he found the girl with bite marks on her head.
Mr Darnell, 32, stabbed the snake until he was able to free the child.
Authorities remained outside the house in the town of Oxford, about 50 miles north-west of Orlando, awaiting a search warrant to remove the snake from the home.