If successful, London Underground will provide full step-free access from street to platform level to benefit mobility impaired passengers, customers with pushchairs and people with heavy luggage.
Work would be completed in 2011.
The Mayor of London, Boris Johnson, said: 'I am determined for every resident and visitor to this city, whether able bodied or with disability, to be able to use public transport safely and easily.
'I have just appointed the legendary Paralympian Dame Tanni Grey-Thompson to the board of Transport for London and I know that she will be delighted to hear of our plans to make Green Park and many more of London's Tube stations step-free.'
London Underground will also be working with Westminster City Council and The Royal Parks to improve the public space around the station which would open up views into the park directly from Piccadilly.
The improvements would provide a larger Piccadilly south side station entrance and direct access from the park.
A modern sheltered paved area on Piccadilly would also be constructed, with a canopy providing cover for passengers waiting for buses and those using the lift.
Richard Parry, Director of Strategy and Service Development for London Underground, said: 'Making Green Park Tube station fully accessible for mobility impaired passengers, customers with pushchairs and heavy luggage and older people is part of London Underground's transformation programme to provide a world class transport system.
'We are working closely with Westminster City Council and The Royal Parks to improve the area around the station - these changes will create a better public space for all those who work, visit or live near Green Park.'
Olympic Delivery Authority (ODA) Chairman John Armitt said: 'From the London 2012 bid right up to the Accessible Transport Strategy we launched earlier this year, we have been committed throughout to delivering the most accessible Games ever.
'It is essential that we provide a wide variety of accessible journey options to and from London 2012 events for spectators, the Games Family, workforce and volunteers so we welcome these plans to make this key station in central London step-free in time for the 2012 Games."
Work to modernise the station has already started and includes installing new CCTV cameras to make passengers feel safer and improve security, putting in Help points and providing a new public address system which will make announcements clearer.
Partially sighted customers will benefit from contrasting handrails and access will be improved for mobility impaired passengers by putting tactile strips on platforms and stairs.
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