The National Day fireworks display is set to take place on Thursday night.
Roads on both sides of Victoria Harbour will close in phases starting at 4pm.
Police says roads in Tsim Sha Tsui will close from 5pm.
Expecting large crowds around Nathan Road and the Cultural Centre, they urge public to choose alternative viewing locations.
Road closures on Hong Kong Island will start earlier, with Golden Bauhinia Square closing at 4pm.
Roads around the Central Harbourfront will close at 6:30pm, gradually expanding to Lung Wo Road and Tim Mei Avenue in Admiralty.
Police also remind the public that land boundary control points will not extend their operating hours and MTR will not extend its service hours.
Temporary cross-boundary bus stops heading to Huanggang and Shenzhen Bay control points are set up outside the West Kowloon High Speed Rail Station.
Cross-boundary bus services in Tsim Sha Tsui and Mong Kok also enhance their frequency as needed.