On the basis of SEM observative results of about 100 samples, the authors describe the SEM charaeterisities of 15 kinds of skeletal mierostructure including caleitic cryp-to-micrograined, crystograined, monocrystal, sheet-fibreus, prismato-fibrous, hyalo-fibro-us, prismatic foliated, aragonitic prismato-fibrous, prismato-sheet-fibrous, crossed, nacreous, apatitic sheet fibrous, foliated fibrous and chalcedony fibrous inicrostructures.The SEM characteristics of skeletal mierostrueture are generally similar to PM ones. There are only a few exceptions in which the sheet fibrous, prismato-fibrous and hyalo-fibrous microstructures composited by calcite are made up of uniform mierograin aligned in stria, normal to shell surface. The cause could be that the calcite is susceptible to etching.Because of different etching-resistant degree, the convexity of various microstrueture elements is also different. It depends on the mineral composition, grain size and organic matrix. The order of the etching-resistance is: siliceous fibrous, phosphoric (foliated fibrous to sheet, fibrous), calcareous (aragonite to calcite). Among the calcareous textural elements, the order is monocrystal, prismatic, crysto-grained, nacreous, crossed (lamellar to fibrous), foliated (lamellar to fibrous), aragonite (prismo-sheet-fi-brous, prismo-fibrous), calcite (prismo-fibrous, sheet fibrous, hyalo-fibrous), crypto-inicrogramed.