Indoor experiments were conducted to investigate the effect of constant light intensity on physiology and ecology characteristics of swimming crab(Portunus trituberculatus).The oxygen consumption rate(OCR),ammonia excretion rate(AER),O：N ratio,lactic acid(LD),energetic contents in hemolymph and respiratory enzyme activities including hexokinase(HK),pyruvate kinase(PK),succinate dehydrogenase(SDH)and lactate dehydrogenase(LDH)were tested in five constant light intensity treatments(0,200,800,1 500,3 500 lx).The main results were as follows:1.Light intensity influenced the OCR and AER significantly(P<0.05).The oxygen consumption rate of the crab under 200-1 500 lx was significantly higher than those of the crab under 0 lx and 3 500 lx(P<0.05).The ammonia excretion rate of the crab under 1 500 lx was significantly lower than others(P<0.05).2.Light intensity influenced total protein,but did not influence other energetic contents and O：N ratio significantly(P>0.05).Our results suggest that protein is used preferentially as energy source.3.Marked differences were found in LD(P<0.05).The LD in muscle of the crab under 1 500 lx was lowest.4.Different light intensity influenced different respiratory enzymes differently.Under 1 500 lx,the activity of HK and PK were at a high level.Glycolysis went faster and produced more energy.The activity of SDH was at a high level,while LDH was low.Aerobic metabolism was at a higher level,providing more energy for a continuous motion of crab The results revealed that light intensity affected respiratory metabolism,and the crab at 1 500 lx had higher metabolism while under less stress.So about 1 500 lx may be the better illumination condition of the crab culture industry.