"main headquarters" is correct and usable in written English.
It is usually used in commercial or business contexts. For example, "The main headquarters of the company are located in New York City."
(Some programs are held outside the main headquarters).
His main headquarters are a loft in the SoHo district of Manhattan.
"The main headquarters of the Hamas movement is in the occupied lands," says Mr Zahar.
It had been linked to his by a bridge and had been his main headquarters.
It was then the main headquarters and logistics base for the guerrilla groups.
By month's end, Mr. McDonald hopes to start moving people back into the bank's main headquarters.
You could call the main headquarters of the party, and immediately they would fix everything".
And Al Qaeda's main headquarters in Pakistan has come under withering attack from the Central Intelligence Agency 's armed drones.
Corinthians supporters during a local futsal championship at their main headquarters in the Bom Retiro neighborhood in São Paulo.
Outside the main headquarters of the separatist movement, an occupied government building in Donetsk, there was confusion at Putin's statement.
American military officials at the main headquarters at Camp Bondsteel said they knew nothing about such complaints.
