One of her corgis is leading part of the parade.
Some 7,000 participants will run through the 60-minute programme which starts at just after 1700BST on Wednesday.
The pageant will feature an eclectic mix of marching bands, carnival floats, choirs, race horses, the Royal Philharmonic Orchestra, camels, dancers, Aberdeen Angus bulls, sheep and chickens.
And the celebration boasts the biggest 100th birthday cake and the biggest 100th birthday card.
The Queen Mother's party on London's Horse Guards Parade, ahead of her birthday on 4 August, also stars pets close to her heart - corgis and dachshunds, her favourite breeds.
One of her corgis is leading part of the parade.
The spectacular finale will see one million rose petals raining down on the Queen Mother and the 12,400 spectators.
The organiser of the ambitious event is Major Michael Parker who has produced the Queen Mother's 90th birthday tribute, the nation's VE and VJ Day 50th anniversary commemorations, and the Royal Tournament.
The Queen Mother is due to arrive for the hour-long pageant in a carriage with a Household Cavalry escort.
Royal salute
She will take the royal salute and inspect the military and Commonwealth participants from her carriage.
After a march-past, there will be a parade of the century, featuring floats, the Finchley Children's Music Group and celebrity guests, including wartime favourite Dame Vera Lynn. Hinge and Brackett and The Wombles.
Hot on their heels will come a parade by the Queen Mother's charities - about 320 groups with which she has campaigned over the years, including the Red Cross, St John Ambulance, Royal British Legion, Mothers' Union and Royal National Lifeboat Institute.
A massed choir including singers from St Paul's Cathedral, Lloyds of London and the City, Christchurch and Magdalen Colleges at Oxford University and the Royal College of Music will perform.
In addition, 25 youngsters from the Royal School of Deaf Children will "sing" in sign language.
Most living holders of the Victoria Cross and George Cross bravery awards will parade in open Rolls-Royces.
Children dressed as cake
Veteran actor Sir John Mills will make a short address followed by the appearance of the Queen Mother's giant, imitation 100th birthday cake.
Thirty children, dressed as pieces of cake, will emerge from the 25ft-high "cake" and hand real cakes to the audience.
Then comes the presentation of the big birthday card signed by everyone taking part in the pageant.
The Queen Mother will celebrate her actual birthday with an appearance on the balcony at Buckingham Palace.