The embodiment of the invention provides a flexible display device and a preparation method of the flexible display device. A flexible substrate of the flexible display device is provided with a firststraight area, a bent area and a second straight area; before bending, a first bending protecting layer is arranged in a bending area of the flexible substrate, so that the bending difficulty can bereduced, and the bending stress can be reduced; after bending, a second bending protecting layer is arranged in the bending area of the flexible substrate, so that creep occurring after the first bending protecting layer is bent can be prevented, meanwhile, a protection role can be further played on the bending area, so that the phenomenon that cracks occur on the flexible substrate and wires on the flexible substrate due to the fact that the protection capacity of a first bending protecting agent for the flexible substrate and a wiring layer arranged on the flexible substrate is reduced is avoided, and further, the display effect of the flexible display device is improved.