The effects of five water temperatures (15.8℃, 21.0℃, 26.6℃, 30.9℃, 36.5℃) on respiration and excretion in three sizes (27.4 g±0.8 g, 276.5 g±17.3 g, and 575.4 g±18.8 g) of hybrid grouper () were investigated using ecological methods in the laboratory. The experimental results showed that both water temperature and body weight had significant effects on oxygen consumption and ammonia excretion rates of hybrid grouper (<0.05). Under controlled laboratory conditions, oxygen consumption and ammonia excretion rates increased initially in all sizes of hybrid grouper, then decreased and increased again as water temperature was increased. These rates were highest at 26.6℃, such as (1.510±0.124) mg/(g·h), (0.306±0.007) mg/(g·h), and (0.161±0.010) mg/(g·h) and (47.739±21.048) μg/(g·h), (13.956±1.783) μg/(g·h), and (6.811±1.882) μg/(g·h), respectively. The regression equations between oxygen consumption rate and ammonia excretion rate and water temperature were quadratic (=1.000). Oxygen consumption and ammonia excretion rates within the temperature range of 15.8-6.5℃ decreased roughly with an increase in body weight at the same water temperature, and the regression equations for oxygen consumption rate mg/(g·h) and ammonia excretion rate μg/(g·h)and body weight were quadratic ( values for the oxygen consumption and ammonia excretion rates in all sizes of hybrid grouper peaked at water temperatures of 21.0-26.6℃ and were at their minimum at 26.6-30.9℃. The mean O/N ratios of the small- and medium- and large-sized hybrid grouper were 21.535, 15.713, and 12.097 to 113.541, 32.193, and 27.094, respectively, indicating that protein, fat, and carbohydrate wereconsumed by the small-sized hybrid grouper for energy, and that protein and fat were consumed by medium-and large-sized hybrid grouper.