Two minutes' silence will be held just before Big Ben chimes midnight as a mark of respect to those who died the Asian tsunami disaster.
The event will promote London's 2012 Olympic bid
Organisers in London say they still want to celebrate the coming of the New Year, but expect a sombre mood.
The disaster donation line number will be flashed across big screens throughout the UK capital.
About 150,000 people are expected to go to London's South Bank to watch a £1m firework display marking the New Year.
London mayor, Ken Livingstone, said: "Tonight London will remember those killed by the tsunami in Asia and beyond.
"We will pledge to do everything in our power to assist the relief effort for those now living in catastrophic conditions.
"Our hearts go out to the thousands of Londoners and other people throughout the world who have lost family members and friends as a result of this calamity," he said.
David Campbell, of Visit London said: "We start out with a minute's silence in respect of all the people who have died and also remembering the people who have got a catastrophic life ahead.
"But I think we still have to mark the start of the New Year, albeit in a different tone than we might have expected a week ago."
Police are warning revellers not to gather in Trafalgar Square, as it can become a hot spot for crime.
The light show starts at 2350 GMT with the London Eye being illuminated with an Olympic theme from 1830 GMT.
'Cold and damp'
Commander Chris Allison, in charge of policing in the City of Westminster, said revellers should check transport times as getting home after the New Year celebrations can be difficult.
He said: "People believe there is something mystical about spending the New Year in Trafalgar Square.
"In reality it is cold, damp, open to the elements, with deep crowds, which unfortunately provides the potential for opportunist crime."
The event, promoting London's 2012 Olympic bid, has been organised by Mayor Ken Livingstone and paid for by the Greater London Authority.
Weather forecasters predict a dry, clear night.
Tubes, buses and the DLR will be running throughout the night and will be free of charge from 2345 GMT until 0430 GMT.