The invention relates to a method for detecting the number of paper on a liquid crystal flat glass production line, which adopts an extremely simple optical fiber sensing mode to detect. A mounting support, an optical fiber sensor, a data optical fiber amplifier and an alarm device and the like are mainly comprised. The mounting support is of an adjustable device and is used for fixing the optical fiber sensor and other equipment in appropriate space positions, and adjusting an optical fiber head to the best detecting angle and distance according to requirement, and the optical fiber sensor especially for detecting paper, glass substrates and the like is used for beam irradiation on objects so as to complete data collection; the data optical fiber amplifier is used for signal processing; and then an alarm is given by electrical control through feedback data or the movement of robots and other corresponding control. The invention can perfectly solve the problems that the robots always grasp two or more packaging paper when the glass substrates are primarily packaged, with the advantages of simplicity, high precision, high sensitivity, high processing speed and the like, and can be suitable for various demanding occasions.