A method and system for appearance inspection of a core of a heat exchanger provided with fins and tubes, performing averaging and dynamic binarization on the imaging data to extract an image of only a tube, then calculating, with respect to the extracted tube image, a center axis across a long direction of the tube comprised of the center coordinates of the tube width direction, comparing the discovered center axis with a reference value to find the maximum displacement across the long direction of the tube, and judging the tube is a defect when the maximum displacement is greater than a predetermined threshold.