The invention discloses a bird nest positioning and early fault warning method for a power transmission tower. The method comprises the steps: 1) acquiring a front color image of the power transmission tower with a bird nest, and carrying out graying and mean filtering on the image; 2) carrying out Otsu segmentation and mapping a target to an original grayscale image so as to obtain a power transmission tower image H; 3) performing Hough straight line detection on the power transmission tower image H to obtain a maximum enclosing rectangle of a cross arm area and coordinates of hanging pointsof insulator strings; 4) creating a sliding template with a similar size, extracting pixel points in a cross arm, calculating a gray level co-occurrence matrix of a template area, and determining a bird nest area; 5) extracting the whole image A marked with the bird nest area, and carrying out ellipse fitting on the bird nest area marked in the whole image A; and 6) calculating the distances between the hanging points and the center point of the bird nest, and finally issuing related precaution affairs or alarms. According to the method, the position of the bird nest is actively located, and the relative distances between the hanging points and the bird nest are calculated.