The invention provides an automatic iron tower inclination angle measuring method based on a machine vision system. The machine vision system comprises an unmanned aerial vehicle carrier, a visual light camera and an identifier measuring device. The automatic measuring method based on the machine vision system comprises the steps that 1, the unmanned aerial vehicle carrier flies to a designated preset position under the control of a flight control system; 2, after the unmanned aerial vehicle carrier flies to the preset position, unmanned aerial vehicle carrier posture adjustment is performed; 3, after the unmanned aerial vehicle carrier reaches a predetermined posture, the visual light camera shoots images, an onboard embedded processor repeatedly reads the shot images and detects red round identifying plates at the upper and lower position of an iron tower; 4, after the two red round identifying plates are successively detected, the onboard embedded processor calculates the inclination angle eta of the iron tower. The visual light camera is carried by utilizing the unmanned aerial vehicle carrier, measurement of the iron tower inclination angle can be automatically completed, the working strength of measurement is reduced, and meanwhile the measurement efficiency is improved.