The carapace exoskeletal structure, and its change during the molt cycle of were studied using hematoxylin-eosin staining and the observation of paraffin sections using scanning electron microscopy (SEM). The results showed that the exoskeleton in the intermolt stage (C) is composed of three sub-layers:epicuticle, exocuticle, and an endocuticle, from the outer to the inner layer. The newly formed epicuticle, exocuticle, and endocuticle in the carapace occur in the late premolt D₄ and postmolt B stages. The exocuticle is in a strongly basophilic state but the endocuticle is in a weak eosinophilic state. The observation by SEM revealed that, in stage C, both exocuticle and endocuticle have lamellae comprised of parallel sheets of chitin-protein fibers, with abundant pore canals (pc). The stacking density of the lamellae in the exocuticle is higher than that in the endocuticle. The lamellae edges of the exocuticle are regular and the pore canals within them are approximately circular. On the other hand, there are rough edges and unequal-sized, fusiform pore canals in the endocuticle. There is a significant change in the ultrastructure in the newly formed exocuticle after molt. In stage D₄,the ultrastructure of the exocuticle is loose, and similar to the old endocuticle from stage C; however, the density of the exocuticle increases in stage A, which may be associated with calcification after molting.