A method of fabricating a flexible substrate assembly includes forming a first polyimide layer on a rigid support base, wherein the step of forming the first polyimide layer includes incorporating in a polyamic acid solution, an adhesion promoting agent and a release agent for achieving different adhesion strength at two opposite sides of the first polyimide layer, and forming a flexible second polyimide layer on the first polyimide layer, the second polyimide layer being adhered in contact with the first polyimide layer, and a peeling strength between the first and second polyimide layers being less than a peeling strength between the first polyimide layer and the support base so that the second polyimide layer is peelable from the first polyimide layer while the first polyimide layer remains adhered in contact with the support base.