The present invention relates generally to a flexible plastic substrate, its manufacturing process and optical components for optical display applications. In so doing, cyclic olefin copolymer (COC) is placed between upper and lower heat-resistant sheets, then heated and pressurized by hot press to form a COC film. Next, the film is subjected to quenching treatment in ice water, and then heat treatment in vacuum drying oven after being placed between two flat plates. Finally, a COC plastic substrate with a high degree of optical penetration, low water permeability and low roughness is shaped, which can be efficiently applied to optical display thanks to its simple processing, lightweight, thin-profile and flexibility.