Scanning electron microscope (SEM) observation shows that Chamidae shell is a kind of bioceramic composite consisting of inorganic aragonite and organic protein materials. The inorganic aragonite distributes in the shell in the form of layers parallel with the surface of the shell. The observation also shows that the aragonite layers consist of numerous aragonite sheets. These aragonite sheets are of long and thin shape and perpendicular to the layers where they are located. More careful observation shows that the aragonite sheets in different aragonite layers possess different orientations, which compose a kind of the interlaced structure of the aragonite sheets. The maximum pullout force of the interlaced structure is investigated and compared with that of the parallel structure of the aragonite sheets based on their microstructural models. The result shows that the maximum pullout force of the interlaced structure is markedly larger than that of the parallel structure. A comparative experiment for the maximum pullout force of both the interlaced and the parallel structures is also conducted, which gives identical conclusion.