An embodiment of the invention discloses an image binarization method and device. The method comprises the following steps: segmenting a grayscale image to be processed into a plurality of image blocks, and calculating binarization threshold values of the plurality of image blocks respectively; carrying out interpolation calculation on the binarization threshold values of the plurality of image blocks respectively through a preset interpolation formula to obtain a binarization threshold value of each row or a binarization threshold value of each line of the plurality of image blocks; and carrying out binarization on the image blocks according to the binarization threshold value of each row or the binarization threshold value of each line of the plurality of image blocks to obtain corresponding binary images. According to the technical scheme, the binarization threshold value is set for each line or each row according to the preset interpolation formula, and pixel points are subjected to binarization according to the binarization threshold value of the line or row, so that a better binarization effect can be ensured; and meanwhile, the binarization threshold values cannot be calculated pixel point by pixel point, thereby reducing calculation amount, saving calculation time and improving binarization efficiency.