The group of some 70 bankers, traders and other professionals said they would support the "Occupy Central" campaign by local activists, which aims to push China to allow free elections in the semi-autonomous city.
Organisers have threatened to block the streets of Central with 10,000 people unless their demands on democracy are met.
The campaign is planned for July, although there have been suggestions it should be postponed until year-end.
The plan has been criticised by both Hong Kong and Chinese officials as well as some business leaders.
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"It is time to speak up for universal suffrage as we are passionate about Hong Kong," fund manager Edward Chin, one of the organisers, told AFP.
Another organiser Au Lai-chong said the group, which will declare its stance in certain newspapers tomorrow, includes both local professionals and expatriates, some of whom plan to join the Occupy protesters on the streets.
"I feel we have to stand up and express our wishes. As Hong Kong citizens we should contribute," said Au, 37, who works for an investment company.
"The current political climate in Hong Kong is having a negative impact on Hong Kong's competitiveness as a major financial centre," it reads.
The group will make several demands, including the protection of free speech, a fair business environment and economic diversity.
The city's political future is a highly charged issue.
China has promised direct elections for its chief executive in 2017, but many pro-democrats fear it will control the choice of candidates to ensure election of a sympathetic official.
Britain returned the financial hub to China in 1997 under a deal that gave it semi-autonomous status and civil liberties not seen in mainland China.