Ewin Freeman, 22, of Solway Road South, Luton, received a 12 month and 44 days sentence when he appeared at Oxford Crown Court.
Judge Peter Ross said Freeman’s actions were of “gross recklessness” that represented a “considerable danger.”
The court also banned Freeman from attending football matches for seven years following the incident at the Kassam Stadium on April 16.
At an earlier hearing in June at Oxford Magistrates’ Court, Freeman admitted to possessing a flare at a sporting event and throwing a missile at a spectators’ area.
He also admitted obstructing or resisting an officer in the execution of their duty and the case was passed to the crown court, which sentenced him on July 21.
In a statement after the case, Oxford United Safety Officer Neil Holdstock said: “Nobody wants to see custodial sentences being issued but it once again shows the seriousness of using flares and pyro at football games and the tough new guidelines that the government and authorities have put in place to try and ensure that everyone coming to the game can do so in a safe environment.
“Fortunately the penny seems to have dropped with most of our own fans who have listened to the messages from the club and from fellow fans that we will not tolerate flares and smoke bombs, home or away.
“Prison and being banned from football for seven years sends a very strong message once again. These things can cause horrific burns and injuries and can scar for life, and we ask all Oxford fans to help us spread the word and make sure they don’t appear at our matches.”
Luton Town FC has been asked for comment.