In lab-experiment to declare the effect of static magnetism on the essential cinnamic oil and comparing its effect with non- magnetic cinnamic essential oil and the insecticide, cymax 50% on 2^nd instar larvae of the cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae). Due to the problems of chemical pesticides to all organisms and environment, natural control replaced pesticides. Results proved that magnetic cinnamic oil is the most effective material than the non- magnetic cinnamic essential oil and the insecticide cymax 50% with LC₅₀ 926.57ppm 4636.11 ppm for magnetic and non- magnetic cinnamic oil, respectively. Although LC₅₀ for cymax 50% was 101.65 ppm, which was lowest than magnetic and non- magnetic cinnamic oil, but the highest concentration of this insecticide caused only 50% mortality for 2^nd instar larvae of S. littoralis, in addition to its toxicity on plants, people and environment. So the magnetism which improved the properties of essential cinnamic oil proved its effectiveness on 2^nd instar larvae of S. littoralis.