Sepia lycidas is a warm-ocean demersal Cephalopoda that inhabits offshore waters at a depth of approximate 15-100 m,and is mainly distributed from the Indian Ocean to the western Pacific,and few research studies have been reported on this species.In order to enrich theoretical knowledge for the artificial breeding of S.lycidas,the fine structure of reproductive system in male and female S.lycidas was observed by anatomical and histological methods.The results showed that the male reproductive system consists of nine parts,i.e.:testis,sperm duct,mucilaginous gland,ejaculatory apparatus gland,middle tunic gland,outer tunic gland,hardening gland,finishing gland,and spermatophoric sac.The sperm duct could be further divided into anterior,middle(ampullae),and posterior part.The mature spermatozoon produced in the testis and transported by the sperm duct,formed sperm masses in the mucilaginous and ejaculatory apparatus gland,then arranged in a new regular in the middle and outer tunic gland,and turned hard in the hardening gland,and formed mature spematophores in the finishing gland.The mature spematophores stored in the spermatophoric sac,and ejaculated outside by batches in the mating seasons.The female reproductive system consists of five parts,i.e.:ovary,oviduct,oviduct gland,a pair of nidamental gland,and a pair of subaltern nidamental gland.Oogenesis is asynchronous,and the oocyte matures by batches,forms a tertiary egg envelope by joint action of the oviduct gland,nidamental gland,and subaltern nidamental gland.The male and female reproduction system of S.lycidas is adapted to its manner of fertilization and spawning.