The invention discloses a system and a method for measuring and analyzing optical density of a spectrum film of a rotary ferrograph. The system comprises a trinocular microscope, an electric object stage, a motor driver, a photoelectric sensor, a trans-impedance amplifier, a multifunctional board card and an upper computer, wherein the trinocular microscope comprises a light source and an object lens, and the electric object stage provided with a limit switch is arranged between the light source and the object lens; a third ocular lens of the trinocular microscope is connected with the photoelectric sensor, an illumination receiving surface of the photoelectric sensor is vertical to a light path of the third ocular lens, and the center of the illumination receiving surface of the photoelectric sensor is arranged on the axis of the light path of the third ocular lens; and the photoelectric sensor is connected with the multifunctional board card by virtue of the trans-impedance amplifier, the multifunctional board card is also respectively connected with the upper computer and the motor driver, and the motor driver is connected with the electric object stage provided with the limit switch. The method disclosed by the invention has the advantages that abrasive particle coverage area percentages at different positions of the spectrum film can be automatically measured, labour intensity of operating personnel is reduced, and testing efficiency and test data accuracy are improved.