Abstract: To learn the effects of Fenvalerate on P450s and protein expression in Tn(Trichoplusia ni) cells, the cells were treated with different concentrations of fenvalerate for 12 h to observe the livability of cells by Trypan Blue and MTT assay. P450s Contends were determined by spectroscopic analysis. Protein maps of controlled and treated groups were analyzed by twodimensional liquid phase chromatographic fractionation (PF2D) after treated Tn cells with 12.5 μM fenvalerate for 12 h. Significant differences in characteristic and mortality of cells were found while the concentration of fenvalerate was over 17.5 μM. P450s activity trended to be enhanced with the increase of time or dose of fenvalerate. The activity of P450s reached a maximum at the dose of 12.5 μM and the time of 12 h, and the value of maximum is (8.562±3.46) nmol/mg and (5.28±1.14) nmol/mg protein. 124 differences points were detected between the 2D maps of treated and controlled groups. 42 points were upregulated and 82 were downregulated. Fenvalerate can induce P450s in Tn cells and those proteins changed after treated with fenvalerate might be related to some receptors in the P450s inducing pathway.