Cytochromes P450, a gene family generally associated with detoxification, was analyzed by real-time fluorescent quantitative PCR (qRT-PCR) in Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae). Our studies showed that the nine p450 genes had different levels of response to tannic acid, and the mRNA expression of six p450s reached the maximum level at the concentration of 1 mg/ml in the midgut of M. troglodyta. Furthermore, the mRNA expression level of Unigene27074_All was 370 times higher than that observed in the controls. Also, the mRNA expressions of CL3273.Contig4_All and Unigene27074_All were induced by 10 mg/ml tannic acid. These findings indicate that p450s have an effect on the metabolism of plant secondary substances by M. troglodyta.