Abstract: The present invention relates to a printed paper identification system for identifying whether a printed paper is a falsified document. The system comprises a paper passage slot and a propeller for driving the printed paper through the passage slot, an identification mechanism having a plurality of light sources and a detecting device installed at two opposite sides of the passage slot, and a controller for actuating the propeller to carry the printed paper through the passage slot, having the detecting device to detect the lights emitted from the light sources and through a predetermined area of the printed paper and generate a correspondent detected signal for each of the light sources, forming one characteristic signal by using the detected signals according to a predetermined procedure, and comparing the characteristic signal with at least one pre-stored identification signal to determine whether the printed paper is a falsified document.