Bone possesses excellent mechanical properties, which are closely related to its favorable microstructures optimized by nature through many centuries. In this work, a scanning electron microscope (SEM) was used to observe the microstructures of a cannon bone. It showed that the bone is a kind of bioceramic composite consisting of hydroxyapatite layers and collagen protein matrix. The hydroxyapatite layers are composed of long and thin hydroxyapatite sheets. The hydroxyapatite sheets in different hydroxyapatite layers distribute along different orientations, which composes a kind of cross microstructure. The maximum pullout force of the cross microstructure was investigated and compared with that of the 0° microstructure with their representative models. The result indicated that the maximum pullout force of the cross microstructure is markedly larger than that of the 0° microstructure.