Fireworks, a gala variety show and Chinese military displays are among the official events planned to coincide with a visit by Chinese President Xi Jinping starting tomorrow for the occasion.
Ahead of the anniversary, state broadcaster China Central Television has been running daily news features extolling what it calls the inextricable ties between China and Hong Kong in fields ranging from sports to the military and the arts.
Underneath the surface, however, tensions are simmering as Hong Kongers, especially the young, chafe at life under the tightening grip of China's Communist leaders.
Law and activists from his Demosisto political party and other groups have targeted a giant flower sculpture bequeathed by Beijing in 1997 that is popular with mainland tourists.
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This evening they staged a sit-in, with some climbing up inside the sculpture, and chanted "No Xi Jinping" before police moved in to arrest them. Two days earlier they had briefly draped the sculpture in black cloth.
Law said there's growing concern that Beijing is steadily eroding the "one country, two systems" principle put in place after it took control of the Asian financial hub.
Under that principle, Hong Kong largely runs its own affairs and enjoys civil liberties unseen on the mainland, but now, he said, "there are lots of people describing the current system as 'one country, 1.5 systems.'"
He and others tick off a list of incidents that stoke fears about China tightening control.
One of the men, Gui Minhai, is still being held.
In a similar case, a Chinese-born tycoon with a Canadian passport went missing earlier this year from his hotel suite.
News reports indicated mainland Chinese security agents operating in Hong Kong abducted him - a violation of the city's constitution.
Myriad other government plans have raised hackles, including stationing Chinese immigration officers in a downtown high-speed rail terminus under construction; setting up a local branch of Beijing's Palace Museum without public consultation; introducing so-called patriotic national education in schools that many parents fear is a cover for pro-Communist brainwashing; and introducing anti-subversion national security legislation.
The wave of buying has been blamed for further inflating housing prices that make Hong Kong one of the world's most unequal places.
"We're supposed to be capitalists - fine. Except when it comes to public auctions of land, when all the big mainland concerns will always win," Mo said.
Xi's three-day visit includes an inspection of People's Liberation Army troops based in the city and culminates in the swearing-in of Hong Kong's new leader Carrie Lam.
China's Communist leaders are eager to tout the success of "one country, two systems," which was envisioned as a way to entice back Taiwan, which Beijing sees as renegade province.
The recent tensions have drawn "serious attention" from Beijing, which can't afford to see pro-independence sentiment in Taiwan and Hong Kong at the same time, said Liu Shanying, political researcher at the Chinese Academy of Social Sciences.
"Therefore, it must be put under control," whether by force or gentler methods, he said.