The unidentified man placed a bet of $20,000 at $3.75 on the odds of Mr Trump being returned to office, and then followed it up with $100,000 at $3.40.
Betting company Sportsbet, who confirmed the bet had been made, is offering $3 on the odds of Mr Trump serving a second term.
It comes after a porn publisher Larry Flynt took out ads in The Washington Post offering $10 million for information that would lead to Mr Trump being removed from office.
The ad states: "The attempt to impeach Donald Trump will strike many as a sour-grapes plot by Democrats to overturn a legitimate election.
"But there is a strong case to be made that the last election was illegitimate in many ways - and that after nine tumultuous months in office, Trump has proven he's dangerously unfit to exercise the extreme power accrued by our new 'unitary executive'.
