According to the obvious deficiencies in the regional division of the traditional gray level-average gray level two-dimensional histogram, an improved regional division method of the gray level-gradient two-dimensional histogram is proposed and meanwhile an Otsu’s threshold segmentation method and its fast recursive algorithms based on improved two-dimensional histogram are given. The experimental results show that this method achieves better anti-noise ability and the regions of segmentation bear a superior consistency, accurate borders and the computing time of the improved Otsu’s method is less than the traditional one.