Abstract: Interactive segmentation, region growing segmentation and thresholding segmentation are studied, which are used widely in image segmentation. These algorithms are applied in some experiments to deal with CT image and the satisfactory results are gotten. The results show that among these algorithms, thresholding segmentation does best in CT image segmentation; in dealing with relatively small images, satisfactory results can be got by using region growing segmentation; although more time will be needed in using interactive segmentation which is the most complex, it dose fairly well with images whose edges are relatively smooth. The evaluation of the three algorithms provides a scientific basis of the application of these algorithms.