The research handles the concept of decadence in the philosophy of Nietzsche, in an attempt to highlight the role of this concept first in Nietzsche's the philosophy of history, then Nietzsche's use of this concept in criticizing Christianity, as Nietzsche saw in Christianity a systematic degeneration when it falsified values and fight human creativity, and invested the values which it called for them to stand against the natural power and natural progress. Finally, this research deals with Nietzsche's attitude which calls for rewriting general history and the actual Christian history.