Carrying out artificial breeding of Octopus tankahkeei is imperative,because of decline of fishery resources and the increasing of market demand.So far,the structure and function of the reproductive system of O.tankahkeei is lack systematic and in-depth understanding.In this study,the reproductive system of O.tankahkeei was observed using anatomical and histological methods,in order to enrich the content of its reproductive biology and provide a theoretical basis for breeding protection.The male reproductive system is composed of spermary,spermaduct,vesicular seminalis,prostate gland,blind sac,spermatophore sac and penis.The lobular type of spermary consists of spermary wall and parenchyma.The vesicular seminalis is classified into three parts artificially:the forepart of vesicular seminalis,the middle of vesicular seminalis and the rear of vesicular seminalis.The forepart of vesicular seminalis is connected with the spermaduct,and the rear of vesicular seminalis is connected with the prostate gland.The spermaduct doesn’t import vesicular seminalis directly,but moves side by side,and then the lumens merge gradually.The wall of the vesicular seminalis is very complex,with two lingulate processes fingering out into the cavity.From the middle of vesicular seminalis to the rear of vesicular seminalis,a lingulate process is getting bigger and bigger while the other one becomes smaller and smaller.A lot of glandular cells are located in the wall of vesicular seminalis and tonguelet.Spermatophore and colloid tail are both formed in the prostate gland,concentrated in the spermatophore sac,and are stored there.The female reproductive system is composed of ovary,oviduct and oviducal gland.Oviduct is long,opening at the funnel mouth.The structure of oviducal gland located on the oviduct is complicated,with a thelycum in it.The discovery of thelycum reveals the mechanism of fertilization which provides practical evidence for artificial breeding of O.tankahkeei.