The present disclosure relates to the field of display, in particular to a composite cover film and a flexible display device. The composite cover film comprises a polyimide layer, and a first hard coating and a first transparent optical adhesive layer disposed on two sides of the polyimide layer, respectively, wherein at least one of the first hard coating and the first transparent optical adhesive layer contains a nanoscale colorant. The present disclosure further relates to a flexible display device comprising a flexible display panel and the composite cover film disposed on a light-exiting side of the flexible display panel.