A circular from the university authorities said those “caught in an intimate position” on the Harare campus would be disciplined.
“In this age to say I’m no longer allowed to kiss or hug someone… is unreasonable,” Tsitsi Mazikana said.
The university has not commented on the students’ objections to the ruling.
It was issued at the beginning of the new academic year as part of a list of “misconducts that attract immediate eviction from halls of residence”.
The list of 11 points also includes bans on squatters and cooking in bedrooms.
Fourth on the list of behaviour that will result in eviction says: “Caught in intimate position (kissing or having sex in public places)”.
Ms Mazikana, who is the students’ gender representative, said that the campus already had strict rules for those fraternising with the opposite sex.
In single-sex hostels, for example, residents were only permitted visitors in the foyer and no visits were permitted after 22:00, she said.
Ms Mazikana said the ban had less to do with morality and more to do with controlling students who were “not happy about the way they are running the university”.
“If they were talking about anything moral they wouldn’t be placing condoms in the hostels and in the clinic, but… kissing and hugging – there’s nothing immoral about that,” she told the BBC’s Newsday programme.
The Zimbabwe National Students Union (Zinasu) said the university administration had a habit of instituting arbitrary rules without consulting student bodies.
The union was organising a petition against the campus kissing ban, Zinasu’s Gift Maposa told the BBC’s Focus on Africa programme.
There were already strict regulations infringing the students’ rights to demonstrate – introduced in 1997 – which instilled a fear of being expelled, he said.
The BBC’s Brian Hungwe in the capital, Harare, says the students often accuse the university authorities of being out of touch with the young.
Beer was banned on campus about seven years ago, which proved very unpopular, he says.