Monosex fish culture is advantageous for fish production and industrial benefits. Therefore, the aim of this study will investigate the control of sex and feminization in cobia ( Rachycentron canadum ) for improving the industrial efficiency. At present, seven fish of cultured masculinized cobia, an average weight of 5.34 ± 0.61 kilograms, has spermiation , but the amount of sperm production is insufficient for artificial insemination. We use LHRH-a2 to enhance sperm production and the effect is significant and average semen amount was up to 1.2 ml per fish. It was enough for cryopreservation and artificial breeding . We succeeded to finish cobia artificial reproduction but failed to culture cobia larvae. We still work hard at cobia artificial reproduction and larvae rearing until 100 days post-hatching to identify the sex ratio of the offspring by gonadal histology, then to confirm the neomale cobia. These neomale fish will spawn with normal female to produce all-female progeny. These results can be applied to cobia aquaculture.