We evaluated the effects of water temperature (12, 16, 20, 24, 28, and 32℃), salinity (5, 10, 15, 20, 25, and 30 ppt) and pH (7.2, 7.7, 8.2, 8.7, 9.2 and 9.7) on oxygen consumption and ammonia excretion in artificially propagated Mugil cephalus juveniles (0.21±0.03 g). The seawater temperature, salinity, and pH were maintained at (19±1)℃, 30, and 7.7, respectively, during the acclimation period. Dissolved oxygen was measured by Winkler`s iodometric method and ammonia was measured using the hypobromite oxidation method. Water temperature had a significant effect on both oxygen consumption rate YO and ammonia excretion rate (YN) and the co-relationship was expressed by the quadratic equations YO=0.0256X2+0.2191X0.1054 (P<0.05) and YN=0.0054X2+0.0441X0.0082(P<0.01), respe- ctively. The oxygen consumption rate and ammonia excretion rate of M. cephalus juveniles increased as water temperature increased and was highest at 24℃, after which the rates decreased. A one-factor analysis of variance revealed that salinity had a significant effect on the oxygen consumption rate (P<0.01). When the salinity was within the range 5–30, the oxygen consumption rate decreased, increased, then decreased again as salinity increased. Conversely, the ammonia excretion rate first increased, then decreased, and was expressed as Y=0.0013X2+ 0.0027X+0.047 (P<0.01). A one-factor analysis of variance revealed that pH also had a significant effect on both oxygen consumption rate and ammonia excretion rate. The oxygen consumption rate and ammonia excretion rate first increased, then decreased as pH increased. The co-relationship was expressed by the quadratic equations Y=0.02583X2+0.198X+0.0775 (P<0.01) and Y=0.02583X2+0.198X+0.0775 (P<0.01), respectively. Water temperature and pH had significant effects on the suffocation point (P<0.01). The salinity also had a significant effect on the suffocation point (P<0.05), but not on the time to suffocation (P>0.05). Our results provide insight into the bioenergetics of M. cephalus juveniles, and provide useful technical parameters for seedling rearing and live transportation.