All seven were convicted earlier this week of assault causing actual bodily harm to Civic Party activist Ken Tsang, but were acquitted of a more serious charge of grievous bodily harm with intent.
Video footage of the attack, filmed by a local network near the city's government headquarters, shocked residents and dented their faith in the usually trusted police force.
It showed a group of men hauling a handcuffed Tsang to a dark corner in a public park, where he was beaten. One man stood over him inflicting blows while others were seen repeatedly kicking him.
It was "a vicious assault", said judge David Dufton as he handed down sentencing at the city's district court, adding that police officers who break the law "have to be made an example of".
The maximum sentence for the lesser assault charges was three years.
"The multiplicity of the injuries and the damage to Hong Kong's reputation... make this a very serious case," said Dufton, noting that the incident had made international headlines.
Police have been criticised for their sometimes heavy-handed treatment of protesters during the 79 days of rallies and street blockades that brought parts of the city to a standstill.
The demonstrators were seeking fully free elections for Hong Kong's future leaders.
Dufton said that Tsang, now 41, was "most fortunate" not to have received more serious injuries from the attack.
The court found that one officer had stamped on Tsang and hit him with a baton, causing circular reddish bruises.
Four other officers kicked him while two other officers did not participate but watched.
One of the officers who kicked Tsang was also found guilty of common assault for slapping him in the face twice after he was taken to a police station.
The defence argued in mitigation that the officers had been under intense pressure during the protests, which they said had dented morale, with a number of police injured.
Defence lawyer Lawrence Lok attributed the assault to "human frailty".
Social worker Tsang was not in court Friday, but pro-democracy demonstrators faced off against supporters of the police outside the building ahead of the sentencing, shouting insults at each other.
Tsang was himself found guilty last year of assaulting and resisting officers on the same night, when he splashed an unspecified liquid on police. He was given a five-week sentence and has said he will appeal.
He has always argued that police brought assault charges against him to distract from the case against them.
Eyewitness? Submit your stories now via social or:
Email: news@pulselive.co.ke
