Biometric hand and eyeball scanners are being installed on the Olympic Park in east London to stop terrorists posing as workmen gaining access to the site.
All 4,500 staff working on the venue for the 2012 games are having a 3-D image taken of their palm and iris.
The unique size and shape of either hand or eye will then be used to ensure workers are who they say they are.
The readers are being installed at every venue in Olympic Park, as well as bridges, roads and perimeters.
Olympic Delivery Authority (ODA) chairman John Armitt said: "As the big build accelerates we are phasing in robust plans to ensure the security the Olympic Park.
"Access controls utilising the latest technology will enable properly authorised, equipped and trained workers to enter and leave the Olympic Park as quickly and safely as possible."
The workforce is expected to double by the end of 2010 as the building work gathers pace, and the ODA says their technology is capable of scanning up to 5,000 workers an hour.
Additional security measures at the site include:
Some estimates put the total security cost of the 2012 games at £1.5bn.
In contrast the security spent on the Atlanta games in 1996 was $150m (£92m).
Olympics Minister Tessa Jowell said: "The UK has years of experience in both tackling terrorism and hosting major sporting and cultural events.
"Ensuring the construction phase of the games is safe and secure is a key part of our preparations for London 2012."
She added: "We are using cutting-edge technology to make sure the workforce and infrastructure continue to be protected."