Police Chief A.C. Roper said the officers, who were not identified, were seasoned veterans but acted in a "shameful" manner.
The video shows police pursuing Anthony Warren's van on Jan. 23, 2008. One officer on foot was hurt when the van swerved through traffic. It overturned on a ramp, ejecting Warren, who lay motionless as officers ran toward him. The video shows them beating him with their fists, feet and a billy club.
An attorney representing Warren in a civil case said he was hospitalized after the chase and didn't realize he'd been beaten until a prosecutor preparing for his trial requested the tape, saw the attack and told the defense about it.
Roper said the department had "terminated 50 years of combined service due to 10 seconds of injustice."
The officers can appeal.
Wendy Crew, an attorney for Warren, filed a claim against the city in March, the first step before filing a lawsuit seeking damages. She said Wednesday the claim was over the "horrific" beating and an attempt to suppress the video of it.
Authorities believe numerous Birmingham officers and as many as a half-dozen supervisors saw the video over the past year, but none reported it.
"In addition to these terminations, we're also reviewing our supervisor's actions, reporting mechanisms and policies," Roper said.
He said supervisors may face discipline, and the Alabama Bureau of Investigation will review possible criminal charges.
District Attorney Brandon Falls said Wednesday the tape of the beating surfaced unexpectedly as prosecutors were preparing to try Warren.
He said prosecutors had a video of the chase "but the beating was not on the copy we had."
Falls said the prosecutor wanted to play the video for the jury but, for technical reasons, she needed another copy and asked for the original.
"We got the original the week before the trial ... and that's where she saw the rest of the tape," he said.
He said they contacted the defense, the Alabama Bureau of Investigation and the Birmingham police chief.
Warren, who was held on $1 million bond after the chase, pleaded guilty in March 2009 to first-degree assault and was sentenced to 20 years in prison. Because of his plea, no trial was held, and Crew said Warren knew about the tape when he pleaded guilty.
Crew said police "deliberately tampered with the evidence" in their handling of the video prior to the criminal trial.
"As horrific as the beating is, the deliberate tampering of evidence is just as horrific," she said.
Crew, who did not represent Warren in the criminal case, said he fled in the van because he was confronted by a man who never identified himself as an officer, was not in uniform and drove after him in an unmarked car. She said he had not been accused of any crime when the pursuit began.
She said Warren, who was hospitalized for a few days after the chase, was "totally unconscious" when he was beaten and did not know it happened until the video surfaced.