[Aim]  To investigate the effect of tannic acid on cytochrome P450s enzyme activity and related gene expression in the pea aphid Acyrthosiphon pisum. [Methods]  3rd and 4th instar pea aphids were treated with tannic acid at doses of 0.5, 1 or 2 g·L^﹣1 for 48 h, respectively. [Results]  Pea aphids fed on broad bean leaves treated with clean water served as the control. The 2.0 g·L^﹣1 tannic acid treatment induced a significant increase in CYP450 enzyme activity in both instars (P < 0.05). Eleven genes in the head were significantly up-regulated after 48 h of tannic acid treatment (P < 0.05), among these the expression levels of ApCYP4C1014, ApCYP4C1019 and ApCYP6A1401 were 3.13-fold, 3.02-fold, and 3.93-fold higher than those of the control, respectively. Fourteen genes were significantly up-regulated in the abdomen, including nine, such as ApCYP4C109 and ApCYP4C1011, which were up-regulated more than 5-fold (P < 0.05). ApCYP4C1021 and ApCYP6A1305 were up-regulated in the mid-gut 2.90-fold and 2.03-fold, respectively (P < 0.05). [Conclusion]  The results suggest that CYP4 and CYP6 family genes may be involved in the metabolism of tannic acid by the pea aphid.