Eason Chung, a member of a student group that played a main role in organising street protests that started nearly two months ago, said today that he and two others had bought plane tickets for the trip.
If they are allowed to enter mainland China, they will go straight to China's legislature to seek talks with Premier Li Keqiang and other officials.
The students have already asked the Hong Kong government's No 2 official as well as former leader Tung Chee-hwa to arrange a meeting but their requests have been rebuffed.
Federation leader Alex Chow and two deputies, Chung and Nathan Law, are scheduled to depart the former British colony for the Chinese capital on a Cathay Pacific flight at 5 pm tomorrow.
They had previously considered going to Beijing during a major summit of Pacific Rim leaders that ended Wednesday but decided against it.
The protesters have been occupying streets in three business and shopping districts to oppose Beijing's decision that a panel screen candidates for the territory's inaugural 2017 elections.