In order to explore the molecular regulation mechanism of Na⁺,K⁺-ATPase(NKA)α-subunit in gills of juvenile Chinese sturgeon at salinity 10,partial NKA α-subunit gene sequence was cloned,and the abundance of α-subunit mRNA,NKA activity,ion concentration and osmolality were examined at 3,6,12,24,48,72,96 hours post-transfer.Results showed that:in experimental group(fresh water-salinity water,FW-SW),the expression of NKA α-subunit mRNA and NKA activity increased significantly(P<0.05)during the adaptation phase(0-12 h),and the concentration of Na⁺,Cl^-and osmolality rose to a maximum level at 12 h post-transfer.In regulatory phase(12-24 h),the amounts of NKA α-subunit mRNA and NKA activity fell to a relatively lower level which was still higher than that of fish in control group(P<0.05).The change both in ion concentration and osmolality were in accordance with the change of NKA and mRNA expression.In conclusion,gill Na⁺,K⁺-ATPase in Chinese sturgeon plays an important role in osmolality regulation by changing αsubunit mRNA expression.The different α-subunit mRNA expression can lead to the variation of enzyme activity which can further regulate the ion concentration and osmolality.