A flexible carbon thin film was prepared by laser induced when phase changing of polyimide thin film. There is no substrate for this thin film. It could be curved at any angle. The electron emission properties of the prepared thin film were measured by a diode mechanism; the thin film was used as a cathode and indium-tin-oxide (ITO) glass as an anode. The turn-on field of the thin film was about 2.1 V/µm. The current density of the thin film was about 150 µA/cm2 at the electric field of 4.5 V/µm. The electron emission measurements indicate that the thin film could be a good candidate electron emission material in flat panel display or be used as other electron source. The morphology and structure of the thin film were investigated by optical microscope and Raman spectroscopy.