Introduction: Coral is a kind of marine cylindrical coelenterate, which is automatically fixed on the calcareous remains of ancestor coral in the white larval stage. Coral is the shell secreted by coral. The chemical composition of coral is mainly CaCO3, which exists in the form of microcrystalline calcite aggregate. There is a certain amount of organic matter in the composition, which is mostly dendritic with vertical stripes on it. There are concentric circles and radial stripes on the cross section of each single coral. The color is often white, but there are also a little blue and black. Coral is not only white.