Abstract: The influence of B(a)P exposure on three different antioxidant enzyme activities and CYP450 gene expression were investigated in sandwormPerinereisaibuhitensiswith body weight of 1.5 g±0.5 g in an indoor experiment. The CYP450 gene expression was shown to be positively related to exposure time and dosage of B(a)P, with up-regulation with time elapse and increase in B(a)P concentration. There was increase in activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) with increase in B(a)P concentration and the exposure time. SOD activity, however, was exhibited by higher concentration of B(a)P, and the activities of CAT and GPx were shown to be positive relation with the B(a)P concentration.