Abstract: In this study, scanning electron microscopy (SEM), X-ray electron spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and amino acid composition analysis were used to comparatively analyze the detailed structure and components of the sclerites of black scaly-foot gastropod collected from the Tiancheng hydrothermal field and white scaly-foot gastropod collected from the Longqi hydrothermal field in the deep-sea environment of the Indian Ocean. The results showed that the main components of the sclerites of both scaly-foot gastropods were protein and water, and the lower the transparency of the sclerites, the lower the water content. In the black scaly-foot gastropod, the lower the transparency of the sclerite, the lower the protein content; while in the white scaly-foot gastropod, the lower the transparency of the sclerite, the higher the protein content. The contents of most amino acids in the sclerites of the black and white scaly-foot gastropods were similar, but the contents of cysteine and methionine were significantly different. The SEM observation results indicated that the sclerites of both gastropod species consisted of an outer layer with densely distributed lamellar tissue in contact with seawater, an inner layer with very sparsely distributed lamellar tissue in contact with tissue, and an intermediate layer with sparsely distributed lamellar tissue. The results of EDS analysis showed that S was distributed throughout the horizontal segmentations of the sclerites; and the distributions of Fe, O and N were remarkably different in the sclerites of the black and white scaly-foot gastropods. In the sclerite of the black scaly-foot gastropod, N, O and Fe were absent in some regions of the outer and inner layers, whereas N, O and Fe were distributed throughout the tissues of the outer and inner layers of the sclerite of the white scaly-foot gastropod, but not in its intermediate layer. The elemental S was one of the forms of S presenting in the sclerites of the scaly-foot gastropods. Fe and S could form compounds with different valence states; and the sulphur-containing amino acids could form different types of compounds or complexes with Fe in the sclerites. The forms of Fe and S present in the sclerites were closely related to the environments inhabited by the scaly-foot gastropods. This study is of great importance for further research into the formation mechanisms of Fe-S biominerals in the marine environment, especially in extreme deep-sea environments.