We investigated that the bioefficacies of cinnamon oil and insecticide based on the mixture of porous starch and cinnamon oil. They were evaluated for their insecticidal activities and their mortality on adults of Sitophilus zeamais. Fumigant toxicity assayed by hanging in glass jars showed that these chemicals caused significant mortality of the test insect. Cinnamon oil evoked high repellent action and high fumigant toxicity (LD50 = 0.030μL/cm3) against adults of Sitophilus zeamais. The two concentrations of the new insecticide 0.030μL/cm3 (LD50) and 0.040μL/cm3 (the highest) lose their insecticidal activity after a minimum of 144h and 168h, respectively. These results suggest that cinnamon oil starch powder is the most effective insecticide, and could increase its efficacy for use as an alternative to synthetic insecticides.