Prosecutor Bruce Kaplan said the sentence is too short.
Twenty-year-old Dharun Ravi could have gotten 10 years behind bars for anti-gay intimidation, invasion of privacy and other crimes.
The case captured headlines across the country in September 2010 when the roommate, Tyler Clementi, committed suicide days after the spying.
Ravi's lawyers are also likely to appeal the conviction, which they say was in error.
