About 300,000 people are expected to leave Hong Kong for Britain using a new visa route which opens on Sunday.
Hong Kong’s British National (Overseas) passport holders and their immediate dependants will be able to apply for the visa using a smartphone app.
About 7,000 people from Hong Kong have already been allowed to settle in the UK since July, the Home Office said.
The Chinese foreign ministry said from 31 January, it will no longer recognise the BNO passport as a travel document.
It will not be accepted as proof of identity either, China said, and they “reserve the right to take further measures”.
The visa was announced in July after China imposed a new security law in Hong Kong.
Beijing has previously warned the UK not to meddle in domestic issues.
Prime Minister Boris Johnson said the move honoured the UK’s “profound ties of history and friendship” with the ex-British colony.
Those who apply and secure the visa will be able to apply for settlement after five years and then British citizenship after a further 12 months.
Although there are 2.9 million citizens eligible to move to the UK, with a further estimated 2.3 million dependants, the government expects about 300,000 people to take up the offer in the first five years.
The 7,000 who have already arrived were allowed to settle before the scheme began by being granted Leave Outside the Rules, which gives the government discretion over immigration rules on compassionate grounds.
Mr Johnson said: “I am immensely proud that we have brought in this new route for Hong Kong BNOs to live, work and make their home in our country.
“In doing so we have honoured our profound ties of history and friendship with the people of Hong Kong, and we h