Since Gustave Reynier, author of Thomas Corneille his life and his theatre(1892), a severe judgement over Thomas Corneille's Tragedies has been making gains. The author who has nothing original was a ingenious imitator of the great trend of his epoch. He classified 16 Tragedies and 1 Tragi-comedy in three categories:Romanesque, Corneilian et Racinian Tragedies. The Tragedies so called Romanesque have a subject and a theme-the disguised identity, the lover between two enemies, etc.-They prevailed in the novel of that epoch and they used the coup de theatre very often. Making profits of the glory of his famous brother, Thomas Corneille later on, moved on to the political and historical theme in vain. He failed to describe the heroism of the past. At the time of Racine, Thomas tempted to adapt once more to the new fashion by simplifying the story in order to observe no more than the movement of the passion. In lack of the talent, however, his style remains clearly inferior to that of his model. Nevertheless, in our opinion, the theme, the subject and the story that the dramatic author employ don't clarify his dramaturgy. The poetic in the Tragedy depends, according to Aristotle, on the way of how the story must be composed. In other terms it depends on the way the author make use of the dramatic elements as subject and theme. What matters once more is the way of producing the tragic sentiment. In this sense, we would like to approach Thomas Corneille's dramaturgy to the purely formal dimension. In order to make this approach, it is necessary to redefine, first of all, the Corneillian and Racinian dramaturgy of romanesque Tragedy. The dramaturgy of romanesque Tragedy is characterized by repetition. Crisis and Coup de theatre are repeated several times. On doing this, the piece is filled up with dramatic tension. In Pierre Corneille's piece, there are two procedures. For the dramatic effect, first of all, he suspend the catastrophe in extremis. Afterwards, on giving the dilemma from the beginning, the blocked situation is made. In this situation, the action which is nothing more than impossibility to act in front of an obstacle, the action is ‘spread' and the tragic sentiment occurs ‘in continuous ways’. In the Racinian piece, on the contrary of the general opinion, his dramaturgy is the same as that of Corneille. There is no turning point in the situation but putting the hero in the dilemma from the very first act, the action is spread and the tragic sentiment occurs in continuous ways. In order to observe Thomas Corneille's dramaturgy, we tried to analyse Timocrate, Laodice and Ariane which represents each of them the three categories as classified by Gustave Reynier. On the contrary of the romanesque trend, Thomas Corneille refrain from repeating rebound and from extraordinary situation. In the dramatical tension plan, he is a real specialist of coup de theatre. In using the disguised identity, in stead of requesting to the deus ex machina, he prepares the inner logic to create the surprise effect in his extreme. The characteristic of his dramaturgy however, resides in the way he forms the turning point to the tragic sentiment. The secret of identity which makes clear at the climax is nothing more than the dilemma of the hero himself. In the difference of Corneille and Racine's procedure in which the dilemma present from the beginning, the action of Thomas Corneille is a quest of a hidden dilemma. In this form, the tragic sentiment produces not in a continuous way but with a strong density at one time. This dramaturgy is at the same time the cause of his success and his oblivion. A tragedy is of all a form but it can also transmit a sense. The sense of a tragedy is formed at the moment when the spectator question himself in his tragic sentiment the sense of the conflict of the heros in front of a transcendental value. The pieces of Corneille and Racine produce this sense continuously while those of Thomas end up at the moment when the sense intervene.