The effects of temperature, salinity, pH and water velocities on oxygen consumption and ammonia excretion of Trachinotus ovatus were determined by the closed flow experimental methods. The results showed that the oxygen consumption and ammonia excretion of juvenile T.[KG-*9]ovatus would be increasing as water temperature increasing, and the volumes reached to a peak value at 27℃. Water temperature had significant effects on oxygen consumption and ammonia excretion (P<0.01).The oxygen consumption and ammonia excretion of juvenile T.ovatus decreased as the salinity increasing, and salinity also had significant effects on the oxygen consumption and ammonia excretion (P<0.01). As the pH increases, the oxygen consumption did not change significantly (P>0.05). The value of pH had a significant effect on the ammonia excretion (P<0.05), the ammonia excretion was increased first, then decreased with pH increasing. Oxygen consumption and ammonia excretion of juvenile T.ovatus increased gradually as water velocity increasing and reached to peak values at 150 ml/min, then decreased gradually as water velocity over 150 ml/min. The effects of water velocities on oxygen consumption and ammonia excretion in juvenile T.ovatus were significant (P<0.01).