Abstract: The subsurface damage of ground K9 specimens and the damage mechanism are studied in this paper. Subsurface damage prediction method and step-by-step etching method are used to measure subsurface damage depth. In addition, cutting depth, feed rate and wheel speed are discussed about the influences on subsurface damage depth. Studies show that, step-by-step etching method is intuitive and effective. For the K9 specimens ground by ourselves, under the experimental conditions in this paper, subsurface damage depth will increase with cutting depth getting deeper or when the feed rate increases. However, wheel speed has no specific influence on subsurface damage depth.