The 100m gold medallist at the 1992 Barcelona Games, who received the sentence in July last year, was present at the Court of Appeal in London for the decision.
He had been cleared of dangerous driving, which he denied, at a trial at Aylesbury Crown Court in Buckinghamshire.But he was disqualified for 15 months and fined £5,000 for careless driving.
Christie, 51, of Sherland Road, Twickenham, west London, crashed head-on into a taxi carrying a newlywed couple while driving the wrong way down a major road.
Two judges dismissed his appeal against the disqualification, but reduced the fine to £3,000.
Mr Justice Treacy, sitting with Mr Justice Blair, announced: “In our judgment this was a bad case of careless driving.
“Mr Christie’s driving can properly be described in our view as bordering on the dangerous.”
Christie, who has no previous convictions, told the Crown Court that he thought he was “going to die” following the late-night collision on the A413 Amersham Road in Chalfont St Peter, Buckinghamshire, on 8 May 2010.
The judges heard that Christie is coaching around 12 athletes for the Olympics, who are undertaking the large amount of driving required while he remains under the ban.