The incident happened when hundreds of protesters inside the university were surrounded by police.
Judge Lily Wong said deterrent sentences are needed for the defendants, Kwok Chun-ming, Ting Pui-kei and Choi Yun-ting.
She said protesters had treated the scene like a “battlefield”, and had committed very serious rioting acts, including throwing bricks and petrol bombs.
The judge said the trio came prepared, wearing protective gear and black clothes, with an incident in Jordan also involving a large area and affecting shops and traffic.
They were given sentences of at least five years.
Meanwhile, a 35-year-old tutor, Yiu Chun-fai, who was convicted of possessing instruments fit for unlawful purposes, was jailed for eight months.
The tutor, along with another 32-year-old man, was earlier cleared of rioting.