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.

Pilot Philip Garvey, 56, his wife Ann, 55, their daughter Emily, 23 and son Daniel, 20 died in the crash near Churchinford, police said.
The family from Woking, Surrey, had been flying towards Dunkeswell Aerodrome in east Devon.
Avon and Somerset Police said the six-seater plane had now been recovered from the field for further examination.
Officers are carrying out a joint investigation with the Air Accidents Investigation Branch.
The family were members of St Dunstan's Catholic Church in Woking.
Emily and Daniel were former pupils of St Dunstan's Primary School and the St John the Baptist School (SJB) in Woking.
A statement released by SJB read: "The family was highly regarded within the SJB community, Emily and Daniel were two of the nicest and kindest young people you could ever wish to meet and were extremely well liked and respected by their peers and teachers.
"Philip and Ann Garvey supported the school in every way, not only in the interest of their own children but also devoting their time supporting the school as a whole even after their children had left.
"Currently Philip Garvey was involved both in supporting our Year 13 students with interview preparation and offering current Year 11 and 12 students work experience at his company - they will be sorely missed.
"Our thoughts, prayers and deepest sympathy are with their remaining family members."
The new air ambulance for Northern Ireland is to be based at the Maze Long Kesh site near Lisburn, County Antrim.
[NEXT_CONCEPT]
Four members of the same family who were killed in a plane crash in Somerset on Saturday have been named.