Abstract: Pyrethroids and organophosphates are commonly used insecticides for the control of lepidoptera pests, including Spodoptera litura, which has developed different level of resistance to these insecticides. Glutathione S-transferases (GSTs) was reported to be widely involved in the resistance to insecticides. Previous study showed that SlGSTO2 was significantly overexpressed in pyrethroid-resistant populations when compared with pyrethroid-susceptible population. To further explore its function, SlGSTO2 was heterologously expressed in E. coli and its metabolic activity to pyrethroids and organophosphates were determined. The antioxidant activity of SlGSTO2 was also determined by disc diffusion assay. Results showed that the recombinant protein of SlGSTO2 had slight metabolic activity to cyhalothrin only in vitro, whereas no metabolic activity to fenvalerate, beta-cypermethrin, chlorpyrifos or phoxim. Compared with LB plate transformed with pET-26b(+), the halo diameter of discs soaked with different concentration of cumene hydroperoxide in the plate transformed with pET-26b(+)/SlGSTO2 decreased significantly, indicating obvious antioxidant activity of SlGSTO2. Findings in this study enriched the function of GSTs genes in Omega class in S. litura.