Student-activist group Scholarism says it will not apply to police for permission before marching to the central government's liaison office on Sunday.
The march - to protest Beijing's refusal to vindicate the June 4, 1989, Tiananmen movement - will be joined with another one arranged by the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, which ends at the government headquarters in Admiralty.
Scholarism members will carry on from Tamar to the liaison office - "where the enemies who produce injustices are".
The group - which rose to prominence last year after its opposition to the government's proposed national-education curriculum - said it believed the right to protest was a basic human right in Hong Kong.
"We didn't apply for 'no-objection' [from police] during last year's rallies, and it proceeded peacefully," said Agnes Chow Ting, the group's spokeswoman.
"We firmly believe the right to march is a basic right that needs no prior registration."
Chow said the group would notify only the police's community relations officers. About half of Scholarism's 400 members and volunteers were below the age of 18, so the group would urge its participants not to physically resist police arrest, she said.
By deciding not to go through police channels, the group is putting its protestors at risk of arrest.
People Power lawmaker Albert Chan Wai-yip, himself awaiting a sentence after being convicted of unlawful assembly, warned that Scholarism might face prosecution.
"They are going to start on a new route from the Tamar destination. The police will have stronger reasons to arrest them," Chan said.
Police said the force had to be notified at least a week ahead of any march of over 30 people.