Changes of hormonal levels during seawater acclimation in Amur sturgeon (Acipenser schrenckii) were studied.Serum prolactin levels decreased continuously with the growing salinity.Serum cortisol levels in Amur sturgeon decreased after transfer from fresh water into seawater in the beginning.Serum cortisol levels in Amur sturgeon increased after transfer into 25 salinity.Serum insulin-like growth factors-I levels changed slightly during seawater acclimation.Serum thyroxine and triiodothyronine in Amur sturgeon increased slightly.Therefore these hormones acted together to promote seawater adaptation in Amur sturgeon.However,prolactin and cortisol were most important.It was feasible to culture Amur sturgeon in seawater after seawater acclimation.