Graphene has received tremendous interest owing to its excellence excellent in electrical conductivity and very high specific surface area. In this work, density functional theory (DFT) is used in order to investigate optical and electrical properties of functionalized graphene which interacted with cypermethrin pesticide molecules. The structures of graphene and pesticide were designed and optimized with M06-2x/6-31G(d,p) method of calculation. Graphene was functionalized by carboxyl, amine and hydroxyl groups to investigate the cypermethrin molecules. The binding energy, band spectra, optical properties and electron distribution of complexes were analyzed. The results reveal that the functionalized graphene with hydroxyl group can highly improve the interaction between graphene and cypermethrin with the lowest binding energy.