A display device and a flexible display screen thereof. The flexible display screen includes a display layer, a flexible cover plate layer, a rigid layer and a buffer layer. The flexible cover plate layer is disposed on a light emitting surface of the display layer. The rigid layer is light-transmitting and is disposed between the display layer and the flexible cover plate layer. The buffer layer is disposed between the display layer and the flexible cover plate layer. And a projection of the buffer layer on the flexible cover plate layer is located at an edge of the flexible cover plate layer.