Dixon, who scored 147 goals for Chelsea, was sentenced on Friday at Luton Crown Court for attacking a man in a pub.
Jailing the 53-year-old, judge Barbara Mensah said the attack was "shocking and sickening to watch".
The judge said the violence was "disproportionate, unnecessary and completely over the top".
Dixon had denied attacking a fellow drinker who had been sitting on a bar stool in the Nags Head pub in Dunstable in Bedfordshire.
The assault on 38-year-old father-of-two Ben Scoble in the early hours of May 15, 2014 was caught on CCTV.
Mr Scoble, a builder, was punched off the stool and then subjected to a flurry of blows while on the floor.
The judge said the shocking footage showed how Mr Dixon launched an attack "out of the blue", which had drawn "a gasp" from jurors when first played to the court during his trial last week.
"You were not just striking him, knocking him off his bar stool, but continuing to strike him when he was on the ground," she said.
"Then you continued to pummel him on the ground."
Dixon, who played for Luton, Reading, Southampton, Millwall, and Doncaster, and earned eight caps for England, had pleaded not guilty to assault occasioning actual bodily harm
He alleged he had acted in self defence, however, Dixon, from Dunstable, was convicted by a jury after a five-day hearing with the judge describing the attack as "completely unprovoked".
Source : PA
Source: PA