Effects of copper toxicity and salinity shock on selective group of juvenile pompano Trachinotus ovatus were investigated. The fish were exposed to different Cu2+ concentrations of 0 (blank), 0.02 (C1), 0.05 (C2), 0.10 (C3), and 0.15 mg·L-1 (C4) at a salinity of 10‰ or 40‰ for 96 h, with the salinity of 29‰ as the control. The results showed that the effects of the acute salinity stimulation to survival rates of pompano between control (29‰) and lower or higher salinity for 96 h were not significant (p>0.05). However, the survival rates in each treatment were decreased with the increase of Cu2+concentration. The dominant factor influencing body moisture of the fish was salinity, and there was no sign that body moisture was correlated with exposure to Cu2+. The gill lamellas in high level of Cu2+concentration (C4 treatments) were abnormal under the salinity of 40‰ and extremely curly under the salinity of 10‰. Hemorrhage in gill was observed in the two C4 treatments. Under transmission electron microscope, pillar cells in gill lamellas appeared deformed and ruptured in some areas of the epithelia in the higher concentration of Cu2+, resulting in the death of the fish due to the destruction of gill tissue, elevation of the arithmetic mean distance from water to blood, the decrease of oxygen diffusion capacity, and other physiological functions. These findings indicate that the pompano might suffer much more pressure when encountered with Cu2+ pollution and low salinity.