Flexible display has attracted much attention from consumer for its light weight, ultra slim, durable and foldable properties. In the last few years, flexible display has evolved from edge curved display to foldable display. Now foldable AMOLED display is widely accepted as a standard configuration of high-tech mobile phone. Advances in polyimide material technology have played an important role in the innovation from rigid display to foldable display. In this article, the basic performance of flexible substrate is introduced, including thermal stability, low thermal expansion, surface performance and small separating force in debonding process. Flexible cover performance is also introduced, including transparency, shock resistance, creep resistance and foldability. Flexible substrate and flexible cover are important application of polyimide in foldable AMOLED. Based on BOE foldable AMOLED development process, this progress report reviews the commercial application development of polyimide material in flexible substrate and cover. Finally, the development tendency of polyimide in display is prospected.