There is no document signaling the existence of Coucy before Roman conquest. It is only in 290 after J.C ., while Maximilian Hercules - anxious with protecting borders of the Empire brought from Germany cultivators' tribes or "Lètes", (where from the name of Ailette, or river " of lètes "), while the name " Codiciacus " or "Cociacus" of latin "Cotia" appears: which means the glade. In effect, to become established, it been necessary to them, to clear a part of the forest of Cuise, which covered the territory of Suessiones, or Soissonais, from the Ardennes to Paris.

The installation of these people had to be made in the place where stands today the village of Coucy-la-Ville. While in the site of Coucy-le-Château, was a Roman establishment, occupied by an officer of the administration, responsible for the surveillance and collection of taxes.

During the barbarian invasions, the region stayed under Roman control until 486, date of the victory, at Soissons of Clovis on Syagrius - governor of the Roman Gaul and the conquest of the earth of Mège by this one. In 500 he made a gift of this territory, which included Coucy, to St Rémi, archbishop of Reims. This one gives it, by testament, to the Church of Reims when he died in 533.

During four centuries Coucy will depend on it. In 922, the archbishop Hervé decides to fortify Coucy, Mouzon and Epernay, who are disposed, in triangle around Reims, on the pretext of protecting the populations of Norman invasions (who had stopped in fact since the treaty of Saint-Clair-sur-Epte) where from consequently the interest of this place, easily defensible.

It is while Herbert, count of Vermandois, succeeds, thanks to certain scheme with the bishops of Soissons and Châlons to introduce his son Hugues, 5-year-old, to become Archbishop of Reims, while the place was made vacant by the death of Seulfe, successor of Hervé. The thing was heard, and approved by the king Raoul and the pope himself. Herbert receives so the temporal administration of bishopric, of which included Coucy.

Two years afterwards, in 927, he kept prisoner the king Charles le Simple, there during rather short time. Then, in 930, he exchanges Coucy for the castle of Vitry, which he had taken to Boson, brother of the king, a year earlier. The Church of Reims loses then any right on Coucy, which rises to the crown in 931, on the death of Boson. Raoul keeps it until 935, time to which he gives it to Hugues the Great, his brother-in-low. This took place while Herbert had been skinned of his lands and of his title by Raoul. Hugues received lands, and Artaud was appointed archbishop of Reims.

Following the death of Raoul, a league forms to overturn his successor: Louis d’Outremer. It consists of, among others, Herbert and Hugues, which lead a fierce war to the king, during almost ten years. But, in 945, Louis take over, at the same time as Artaud takes over Coucy. Though, he keeps it only one year, because an ancient ally of Hugues, Thibault le Tricheur, count of Chartres and Blois, wins the fortress by the corruption of the garrison. Artaud recaptures it, in 958,  and gives it to Eudes, son of Thibault immediately, in exchange of a 60-pence census.

Coucy passes then from hands to hands: Eudes gives it probably in 978 to Théodoric, one of his sons. Then in 1037, chronicles mention Lion, friend or vassal of Eudes, died in the battle of Bar-le-Duc. Finally, in 1059, there are traces of Albéric or Aubri de Coucy. He is married to Ade de Marle who will betray him in favour of Enguerran, son of Dreux of Boves, with the help of whom she will make her husband prisoner. This one will earn his freedom only in exchange for its lands. Disinherited, this last will leave in England to join William the Conqueror who will donate him a land in the county of York.