A US military translator at the US base in Guantanamo, Cuba, arrested 23 July, does not face the possibility of the death penalty, the Air Force said in a statement.
Ahmad al-Halabi was formally charged on Thursday with espionage and aiding the enemy.
He was also charged with making false official statements; retaining documents without authority and a fraudulent credit application scheme.
Prosecutors said al-Halabi aided the enemy by attempting to send information about the prisoners and the Guantanamo facility to Syria. He is now in pre-trial detention at Vandenberg Air Force Base in California.
In a statement, Major General Paul Essex said al-Halabi would be court-marshalled at Travis Air Force Base in California, but no date was immediately given.
Two other people suspected of espionage, a chaplain and another translator who worked at Guantanamo, have been arrested.
Army chaplain Captain James Yee, a Muslim convert who taught English in Syria, was arrested 20 September on suspicion of espionage at the base and is being held at a prison in Charleston, South Carolina.
Ahmad Mahalba, a naturalised US citizen of Egyptian descent, was arrested on Monday after compact discs with what appeared to be classified information were found in his luggage at Boston's Logan airport during a routine inspection.
Some 650 prisoners, most captured in Afghanistan as part of the US’ so-called "war on terror," are being held at the base at Guantanamo, on Cuba's south-eastern tip.