Abstract: Taking Thryssa hamiltonii as sample, we studied the toxicity of di-n-butyl phthalate (DBP) on marine epipelagic organism. The results show that the 24 h, 48 hand 96 h LC50 value of DBP on T. hamiltonii is 3.75 mgL-1, 1.52 mgL-1 and 0.94 mg.L-1, respectively. The safe concentration (SC) of DBP on T. hamiltonii is 0.07 mg.L-1. Compared with the control, at 24th hour, the superoxide dismutase (SOD) activity of visceral mass is induced at 0.07 mg.L-1 and inhibited at 0.55 mg.L-1; while at 72nd hour it is inhibited at 0.07 mg.L-1 and induced at 0.14 mg.L-1, and there is no significant difference among the other groups. The SOD activity in brain increases at 24th hour and reduces at 72nd hour. Under DBP exposure, the malondialdehyde (MDA) content obviously increases at 24th hour in those 2 tissues. The acetylcholinesterase (AChE) activity is induced at 0.07 mg.L-1 and inhibited at high dose in visceral mass; as for the brain, it is induced first at 0.55 mg.L-1 and inhibited afterwards, but it is induced in the other groups all the time. Therefore, DBP, which has obvious toxic effects on T.hamiltonii, is harmful to marine life, and it should be paid attention to its potential ecological risks on marine environment.