Land is being made available by Northern Ireland Executive.
One of two helicopters that will form part of the service toured Northern Ireland last week. The charity behind it says it hopes it will be fully operational by March next year.
The decision to choose the Maze site has been waiting for executive approval for some time.
It was given the green light following a test landing last week, which was used to assess several factors, including noise levels.
Northern Ireland was previously the only area in the UK without a HEMS (helicopter emergency medical service).
In March, the then health minister, Simon Hamilton said the air ambulance would be based at Belfast International Airport.
But the charity behind the new service believes basing it at the Maze will be cost effective.
It plans to use an existing building that was once used to check vehicles.
The helicopter has arrived after a campaign for an air ambulance service by the late Dr John Hinds.
Dr Hinds died in an accident in July 2015, but his partner Dr Janet Acheson continued his campaigning work.
The building at the Maze will be converted into hangar space for two helicopters, as well as changing facilities for crew and an operations room.
The charity Air Ambulance Northern Ireland says it will need to raise about Â£2m a year to operate the service.
Health officials have yet to decide if it will have doctors onboard as well as paramedics.
The new air ambulance for Northern Ireland is to be based at the Maze Long Kesh site near Lisburn, County Antrim.