The present study was carried out to investigate the toxic effect of some pesticides (Lambda-cyhalothrine, methomyl, Carbofuran, Chloropyrifos and Mancozeb) against cotton leaf worm Spodoptera Littoralis. Different samples of peanut, linseed and sunflower seeds were collected, extracted, cleaned up, to use in different studies (toxicity analytical and determination joint action effect of oil peanut extracted with pesticides against S. Littoralis. The pesticides residues mixed with oil extracted, were determined using biochemical's parameters (Acetyl cholinesterase activity). Thin-layer chromatography was used to separate the tested pesticides from each compound. RF values for the tested compounds were recorded alone and in their mixtures with non treated oils. Pesticides residues extracted from the treated samples of peanut, linseed and sunflower seeds oil were determined after studying their effects on Acetyl cholinesterase activities. Results showed that Chloropyrifos insecticide was the most potent compound followed by Lambda-cyhalothrin, Methomyl and Carbofurn. Mancozeb and oil peanut have no toxic effect on S. Littoralis. The joint action effects resulting form mixing oil peanut with each of the tested compounds are shown that synergism was noticed with oil peanut in combination with Methomyl, Chloropyrifos and Lambda respectively.