In this paper,the gill Na⁺/K⁺-ATPase (NKA) activity and the body moisture in juvenile grey mullet Mugil cephalus were investigated after 12 d stress at different ambient salinities (0-40).The results showed that the mortality rate of the juvenile grey mullet were 31.7%,28.3%,6.7%,3.3% and 13.4%,respectively when the fishes were suddenly transferred from control group(salinity was 33) into S₀(salinity was 0),S₁₀,S₂₀,S₃₃ (control) and S₄₀ treatments.The gill NKA activity fluctuated in the first 3 d,and then changed smooth1y in all treatments.At the end of experiment (12 d),the NKA activity varied with salinity grade in a ″∩ ″shape,being significantly higher in salinity S₁₀ and S₂₀ (P<0.05) groups while the lowest in S₃₃ group.The body moisture content of visceral removal group showed a trend of S₀ > S₂₀ > S₁₀ > S₃₃ > S₄₀ while that of whole fish group showed a trend of S₀ > S₂₀ > S₁₀ > S₃₃ > S₄₀.All the results revealed that the juvenile grey mullet could adapt to different salinity environments in 9 days.Comparing with the visceral removal group (14 d),the moisture content of whole fish group (12 d) was higher except for the S₀ treatment group.