Abstract: With SKW-3 instrument, we determined the oxygen consumption (OC) of gill tissue in vitro and of per unit respiratory area gill tissue in vitro of juvenile Trachinotus ovatus to investigate the effects of temperature, salinity and pH on them. The results reveal that with the increase of temperature, salinity and pH, the OC of gill tissue in vitro and of per unit respiratory area gill tissue in vitro of juvenile T.ovatus increase. Under the conditions of water temperature 27 ℃, salinity 28 and pH 8.5, the OC of gill tissue in vitro reaches the maximum value but then declines gradually; under the conditions of water temperature 27 ℃, salinity 23 and pH 8.5, the OC of per unit respiratory area gill tissue in vitro has the same situation as above. Water temperature, salinity and pH have significant effects on the OC of gill tissue in vitro (P0.05); temperature and salinity have very significant effects on the OC of per unit respiratory area (P0.01); pH has significant effect on the OC of per unit respiratory area (P0.05). There is no significant difference in the effects of salinity 18 and 33 on the OC of gill tissue in vitro of juvenile T.ovatus (P 0.05).