The temporary route will spare spectators leaving the exhibition venue a 750 metre walk to the nearest crossing point and is hoped will help ease footfall.
Excel will be one of the busiest venues throughout the Olympic and Paralympic Games, staging 13 events in total.
Built from reused shipping containers, the pontoon was put to the test last week for the WorldSkills London 2011 event. It is fitted with a 15 metre gate to allow boats to pass.
A new footpath at Silvertown Quay and a temporary bridge across North Woolwich Road will also be erected to lead sports fans to Pontoon Dock DLR station.
Transport for London’s Docklands Light Railway director Jonathan Fox said: "We're looking forward to playing a big role in getting people to and from the 2012 Games venues, and this walkway will mean even more of our stations will play a part in that."
The Mayor's office announced last week it will be sponsored by global airline Emirates in a ten-year deal worth £36m. It will carry up to 2,500 people per hour in each direction, creating a direct link between The O2 and Excel.
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