Abstract: Symbiosis and calcification are the most important issues in the coral ecology. To understand more biological process of coral symbiosis and calcification the coral Galaxea fascicularis was used as a model on which the coral-morphological characteristics of symbiont cells and skeletons were studied with transmission electron microscope (TEM) and scanning electron micrograph (SEM). It showed that the outer membrane layer and the inner membrane layer of the coral symbiont were originated from the host cells and the zooxanthellae cells, respectively. The complex structures of the coral symbiotic membranes played roles in the metabolite exchange and interaction in the couple of coralzooxanthellae. Coral skin cells could secrete a large amount of mucus and had a certain fluidity on the coral surface, which might be related to a shuttle dynamic of symbiotic zooxanthellae or microorganisms. In addition, the coral skeletal microstructures indicated that the secretion of organic matrix (SOM) was critical for the formation of the calcified crystals and skeletal fibers, supporting the viewpoint that coral mineralization is a biological regulation process. This study provides us further understanding of the coral morphology for the study of cellular stress responding to the marine environmental changes.